Using Fuel Trim to identify type of misfire (can it be done?)
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- Опубликовано: 28 авг 2024
- I in this video I am comparing two different cars. A 2000 Lexus RX300 with a wideband O2 sensor and a 2004 Dodge Neon with a narrow band O2 sensor. I created a no fuel misfire and an ignition misfire on both systems. I am NOT teaching wideband/narrow band O2 operation here, just fuel trim reaction to a misfire. Finally, there is another variable to misfire diagnosis using the oxygen sensor and fuel trim and it has to do with the oxygen sensor itself. Does an O2 sensor actually sense oxygen or fuel? Another question to ask yourself is, does unburned fuel in the exhaust affect the oxygen sensor's signal? The answer to this is absolutely yes! You can see it in this video and my explanation of volume of oxygen in the cylinder is incorrect. The reason there was a difference between the no fuel misfire and ignition misfire was because of the fuel leftover in the exhaust.
Here is a video from my premium channel I've titled "the tomato sensor" • Video
Engine Performance Diagnostics chapters 4 and 5
Tools used
- scan tool
Playlist
- (Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing
• (Chapters 4 and 5) Fue...
Related videos
- the "tomato sensor
• Video
- fuel trim
• Operation of an oxygen...
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Scanner danner is a blessing to all mechanic's I'm a ASE master tech but I get rusty and his video's help refresh my memory as well as learn new techniques. Thank you MR Danner. ✌️
After 10 years I'm getting back into auto mechanics and Diagnostics... Thank you for the teachings💯
There are a number of excellent automotive teachers on youtube, and I have learned from and have been helped by many. But you, Scanner Danner, stand alone as far and away THE BEST. I look forward to buying and reading your book, and to subscribing to your premium channel. I have no doubt both will be worth every penny and far more.
Thanks so much Ron! You truly made my day.
Thanks for your input. If I could get past all the bashing I would. I agree with you about some misunderstandings I may have with the O2 sensor and how it actually works. When I can put all of this together I will do a follow-up video to this. The main point of this video was to show that an ignition misfire does not cause a rich condition and negative fuel trim numbers. I would like to hear about your bad cylinder negative fuel trim scenario. Thanks again for your time and comment
This is not a difficult concept to understand. Especially if you know that an oxygen sensor is exactly that, a sensor that reacts to oxygen.
The term "rich" when discussing fuel trims, and fuel mixtures in general, is probably where most of the misconceptions come from. People I've worked with don't realize that rich isn't rich. Rich is oxygen deficient.
Oxygen deficiency can occur for many reasons but at no time can an oxygen sensor determine if a system has more fuel than it's supposed to have.
Great video.
I work in developing software for ECUs and I like how ScannerDanner presents such topics in simple and interesting way.. Even after 11 years this channel is my favorite. Great job
Thank you so much!
Very well explained! Still interesting why the fuel trim goes up. It is much easier to remember things like this if you understand every detail
You had it right in your comments on the ETCG video. I just felt the need to do this to clear the air for those that think an O2 will go rich with an ignition/compression misfire, from unburned, raw fuel in the exhaust. As you know, as misfire will drive the O2 lean regardless of the type of misfire.
Thanks for the comment and great advice to the other poster on ETCG.
Yesterday, one of the techs in my shop was diagnosing a surge at idle and an intermittent stalling issue. He had codes for a small leak and oxygen sensors. He was trying to command the vent valve close to see if it could see an increase in fuel tank pressure, but at some point saw negative pressure. He was trying to associate the vent valve with the surge, but I could not see the surge as a symptom of a restricted vent valve. Today, another tech looked at it and checked one spark plug and the electrode was eaten away. Guess what, the LTFT and STFT were single digit negative.
Logically, they should not be negative, but they were. Love your videos as always.
Thank you very much for the compliment. I am glad you like them. Keep watching, I am working on more everyday.
Paul (ScannerDanner)
Paul, I had a citeron c3 1.6 8v in yesterday with inj no 4 open circuit DTC stored. Checked the STFT and that was 23%.checked it on the gas analyser and the HC were very low which confirmed that the injector wasn't working. Removed the plug and found corrosion on the terminals. Checked resistance 2.2 against the other 3 of 13ohms. Replaced the injector which brought the fuel trims back in line. Your videos help me so much! Keep up the excellent work!
I'm going to jump in and answer this since no one else has yet. I don't know what you mean by Internal v. External problem is. As his name implies, his video is about not using the scanner to diagnose a misfire. Quick checks would be examining the spark plug, wires and the boots, checking fire and voltage to and from the coil(s), checking for voltage signals to the injectors and feeling each injector to see if it is firing. Do a balance-of-power to find the faulty cylinder. (continued)
I just used this to find a stuck injector on a 3.4 gm. Buddy had a miss. He replaced plugs/wire. Still missing. Used fuel trims to see it was running lean, then scoped the injectors and looked for a missing pintle hump. He had been driving like that for 6 months cause he couldn't figure it out. I fixed it in 45 minutes thanks to Danners channel.
nice! Thanks man
Logical and intelligent analysis.. About note the height of fuel tirm in the case of no fuel misfire compared to the case of Ignition misfire.. Thanks Scanner Danner
This is (another) illuminating seminar, Paul. It also gets to the semantic issue of what we define as rich and lean -- a little confusing when you think about it....
I like this guy. I'm an ME (but not in the automotive industry), and I do ALL of the work on my '08 Acura TL Type-S. A few weeks ago, a spark plug decided to take a shit, which triggered the MIL, followed by a surprising loss of power and the embarassement of limping my "garage queen" back home with her sounding like a fucking golf-cart. And a top speed to match.
During my _LONG_ drive back to the house I was imagining every scenario possible as to what the issue might be, how much it would cost and how much back pain I would suffer while digging down to the troublesome part. Bad injector? Bad coil pack? Some pissy connector somewhere?
I kept thinking about how a misfiring cylinder would affect the AFR and how I could use that info to help me pinpoint and solve the problem quicker. I was wrong. Way wrong. I wish I had seen this video before I fucked around and wasted time trying to diagnose the problem based upon incorrect assumptions about how different types of misfires would affect STFT and LTFT! Some simple, old-fashioned troubleshooting led me to the correct diagnosis.
Nice job on the video dude. I have been re-edu-muckated...
Great vids man!!! you're the best!!! when the coil is unplugged, the mixture doesn't burn, hence the Oxygen stays raw, and the O2 sensor picks it up and tries to add more fuel to compensate. When fuel is cut, you have raw more Oxygen (taking the space of fuel as stated by yourself) so higher trims...
Cheers!!!!
Thank you for the comment. The Picoscope I am using is the 4000 series automotive 4 channel. It is awesome isn't it?
Nothing wrong with the MT2500, you won't need a Verus if you got a Pico. Look into the Solus Ultra when it comes time to upgrade the scanner.
I just stumbled across your videos for the first time and it is very refreshing to find someone posting videos on here that actually knows what they are talking about! And it still kind of amazes me that people forget that o2 senors measure the oxygen and they forget, or fail to realize, that the oxygen is no longer being burnt so even though there is excessive HC in the exhaust there is also a raised O2 level now. But anyways great videos and keep up the great posts.
thanks for this information..I've always been led to believe the theory about lean and rich misfires, thanks for the clarification
you didn't need help, you got it :-)
One thing I was trying to cover in the video was that ignition misfires DO NOT make the O2 go rich and cause negative fuel trim numbers. There is another guy here on youtube that "trains" people that was claiming that to be the case.
Thanks ! This puts us on the best diagnostic path . Very helpful ! Now we know !! 👊🏼
That is correct. Although there is some debate in this field as to the O2 sensor signal being affected by hydrocarbons. I am not debating that at this time as I am no chemist. But what we can definitely determine from this video is BOTH types of misfires drive the O2 signal lean due to excess oxygen in the exhaust. With the injector (no fuel) misfire showing even more lean. One other thing, unburned fuel IS NOT rich. This is a very common misconception in this field.
Thanks Danner great work, ive been trying to research this for years, God bless
I am man enough to admit that i was wrong and you have shown me the light brother!i guess the reason i thought this was valid was because most of the cars i have checked have had fuel injector problems so when i saw the positive fuel trim i thought it was right.thanks again bro,GOD bless!
Hey, no problem bro. I didn't do this video to prove anyone wrong, I actually did it for me too as I had some doubts as to the result. When you get a chance, check out sections 4 and 5 in my book (now that you have it). These two chapters cover O2 sensors and Fuel trim in great detail. I think it will help back up this video.
I’m new here. I’ve been experiencing rough idle with my 14 jeep Cherokee 4 cylinder. Using the bluedriver scanner. I found the LTFT at 19% and STFT at -4%. Replaced spark plugs and injectors with mopar. Rough idle is still there. Cleaned throttle body. Still there. Now i gotta check fuel injectors. This video really clarified alot
Does your LTFT improve at 3000 rpm in park?
@@ScannerDanner yes. I see better long term at 1500rpm
@@ravit928 sounds like a vacuum leak
@@ScannerDanner thanks a lot for the feed back. I’m a tech at mazda. New to the auto field and your video helps a lot understanding these diagnostics. I’m gonna try and find this leak with a smoke machine. I have a feeling the EGR valve is clogged. I don’t have any DTCs. And when looking at mode 6. I get random misfires. Cylinder 1-4 gives me random numbers from 0-19 on random days when i check. I cleaned my throttle body and after doing a 20 min drive i saw low misfire like c1-3 c2-5 c3-0 c4-8. Then another week. The numbers change
Update. Smoked intake. Found no leaks. Pulled fuel injectors and check ohms. They were all good. Sprayed them down with brake cleaner. And reinstalled. Drove for about 20min. Checked LTFT went down from 19 to 3%. Definitely injectors
You are absolutely correct that neither ign. nor lack of fuel misfires cause a rich condition. The reason being that people forget that there is a full cyl. worth of O2 going in there also, and even with the ign misfire and unburned fuel, the O2 content far out weighs the amount of fuel. Both misfires cause a lean condition and will drive trims rich. You come back on IATN and you wont be bashed, I'll see to it. Remember, one can't feel, see, or hear emotion online, so don't take things personal.
This is definitely Vital Information, that I was not aware of with the Fuel Trims. Keep the info Coming ! ! !
My car is running rich on one side of the engine bank 2, yet the O2 sensor on the same side bank 2 is reading lean. My right side catalytic converter is shooting out a lot of black soot. It definitely has a misfire because the MIL is flashing. I have changed out the O2 sensors, spark plugs, cables, cap/rotor, fuel pump, fuel filter, EGR, gas regulator, MAP, & finally the MAF sensors. Watching this video made me realize it might be clogged fuel injector making the O2 sensor read a false lean.
Going way back in the library and still learning to think outside the box today
I think ScannerDanner is a great guy as a tech and as a teacher keep it up with this great work !!
Thank you!
I couldn't have said it better myself! Nice job.
Excellent excellent subject matter to cover.. Now I see the error in my ways of using fuel trim to diagnose misfire.. Thanks Dan u are the greatest!!
I will check those sensors' connectors, thank you. Right now I am waiting for parts, we did a fuel pressure test and it does not holds pressure at all. Well, thank you, nice talking to you.
You switched the position of the LT and ST fuel trim graphs for the second car. Made my brain go into open loop there for a second or two.
You said it man,depends on many variables like COP , wast spark,distributor,misfire code or not,how accessible is the cylinder in question,how easy it is to current ramp etc.But if a gas analyzer is available ,I think wold be my first choice like you did with Eric.I had a Cadillac with North star engine in my shop today.No crank.To check for voltage drop at starter I had to remove the intake manifold,The cable was fine so I replace the starter.So it depends on the task at hand.LOL
Thanks again
Hey scannerdanner just wanted to talk to you about a test like this using the map sensor and O2 sensors data to find a type of cylinder miss. you might already know about this and if so just let me know. its pretty much what your doing but little different. so here we go first to determine if its a possible mechanical miss look at the map sensor data. were using the map sensor as a vaccum guage. so if the map looks smooth not jumping around like you see on vaccum guage with mechanical problem then look at o2 sensors. upstream and down stream. mainly downstream is what will help lead you in right direction to a fuel issue or ignition issue. now lets say downstream o2 is reading lean this will lead you to a fuel issue because the cat is letting go of this extra o2 that doesn't need to store since the injector isn't supplying fuel. now vise versa if the downstream is reading rich now were looking at an ignition miss because now the cat is using all the oxygen to burn off all the extra fuel. now its a great test I was taught by a very smart instructor like yourself and wanted to share with you if you didn't know about this. if so just let me know. if you know about this and or have video of this I would like to know. thanks and keep the great vids coming.
Thanks so much for sharing. That is a great tip!
Mate your channel is awesome, you explained what the data was all about on the display on my Bosch 2220 found my no2 bank in my ford xr6 BA STFT was 30 it's idle has been really rough, also in my Ford AU I found inlet manifold Inlet gasket leak so I'm guessing it's the same with my BA as well, ruddy cars!
Thank you my friend, I will. Spent all day reading about the tomato :)
Chemistry is difficult for me to understand, especially the stuff that is being talked about in a lot of the tomato threads.
Hi Paul, At AVI on demand, instructors Ron Bilyeau and Bill Fulton are both sure that the type of misfire can be determined by the fuel trims: saying that a rich density misfire will cause negative double digit fuel trim numbers and a lean misfire will cause positive double digit numbers and also that the rear o2 sensor can can indicate types of misfire: high mv is an ignition misfire while low mv is no fuel misfire.
This was an argument against others who were stating that an ignition misfire will drive fuel trims negative.
Yes, fuel trim can be used as an aid to the type of misfire. In fact you can see the difference in fuel trim between the two. Also, I agree in using the downstream O2 as well!
@@ScannerDanner ive found your video very informative im having a po300 random misfire on my 2004 silverado 1500 with the 4.3 v6 it only happens on the highway in 3rd or 4th gear going up hill or towing my camper i can floor it in 1st or second no problem with no issue. I logged my upstream o2 sensors and my short term fuel trims. At the moment of misfire the o2s are reading very rich like .8-.9 and the short term fuel trims go completely flat during the misfire. Normally they fluctuate from -3 to +5 in the typical up and down fashion, but go dead flat around 0. Any idea what would cause this?
@@dougsavery5442 any misfire will alter your fuel trim and O2 readings. So that info isn't really all that helpful. From your description it sounds like a secondary ignition issue. Hard to say, but that flat style distributor cap was notorious for crossfiring inside.
Thanks! Some GDI systems are certainly on my radar.
I copied this from my book.
Higher than normal fuel psi,
Ruptured fuel psi reg. diaphragm,
Leaking fuel injector,
EVAP purge problems,
ECT or IAT sensor problems,
MAP/BARO or MAF sensor problems,
EGR valve stuck open at idle,
Fuel contaminated oil,
Head gasket leaking causing coolant contamination of the O2,
Jumped timing chain/belt
Thanks for clearing that up, Paul. Very good video. Even though the system went open loop on the narrow band, you could probably see the O2 sensor voltage PID and see that it was indicating lean. In fact, I wonder what the O2 voltage would look like on forced open loop system with an engine misfire? Can't wait to see your video on wide band and how the ECU knows the cat is bad on that system since it really can't compare front and rear o2 voltages.
This is just the scanner portion of the Verus I am using. You can do the same thing with ANY cheap scanner you just may not be able to graph the data.
Hands down, best channel of it"s kind. I"ve got a P0300 DTC, along with flashing check engine light, that is intermittent.Shortly after the event occured, st fuel trim went up to 25%, and then got to 0%, and the voltage of both (upstream and downsream) o2 sensors went to about 0,03v, and 0,2v respectively. But because the fault was intermittent, as soon as the engine management light turned off, the upstream o2 sensor voltage would start oscilate normally, and the voltage of the downstream o2 went back to about 0,7v.(narrow band, as far as I know). What I can"t understand is why the stft stays at 0%, even when the upstream sensor"s voltage starts to oscilate normally? Allthough at first i suspected the sensor, then i thought that it had to go into open loop, and that was likely why the stft went to 0%. But I still don"t know what to make of the low voltage on both sensors, when the check engine light is blinking, followed by the normality of the voltage value on both sensors, when the check engine light turns off, becouse at the same time the stft remains at 0% at this later moment. So, if I was to say that the voltage comes back becouse it briefly reenters into closed loop, shouldn"t then the stft start to show a value other than 0%? Your video guids me towards the conclussion that tere is a greater lean condition than i thought that forces the emcu to go in open loop, thus one or even more injectors at fault(given the p0300). I know it"s not your job to answer this kind of questions, but I desperatly seek any help i can get in order to try to fix it on my own, given that for the moment it is not safe to wonder arround autoshops, with the pandemic still on a crescent trend in my country.
Remember that a misfire will cause a false lean condition and will elevate your fuel trim numbers. If you can feel the misfire at idle, perform a cylinder drop or rpm drop test to figure out what cylinder is misfiring and focus there. The O2 and fuel trim issue you described sounds like an effect of the misfire and not a cause
@@ScannerDanner first of all, sir, I sincerely apreciate the fact that you took the time to read this and whrite a replay, and promptly too. Thank you! Did the drop test, and allthough there was a difference with each cylinder test, there allso seemd to be a difference between how the engine(4 cylinder engine that is) reacted when 1 and 2 were tested(drop in rpm with each one) and how it reacted when 3 and 4 were tested( engine stalled; plugs for each coil was disconected the same amount of time ).
@@traiansandulescu5051 so engine got rough with cylinders 1 and 2 but severely rough with cylinders 3 and 4? What are we working on? Year, make model, engine etc
@@ScannerDanner waw, thank you, sir, you are being kind.May GOD bless you and your family! WOULD LIKE TO MAKE SOME SORT OF PAYMENT FOR YOUR VALUABLE INPUT, SO, I'VE JUST SUBSCRIBED YOUR PAID CHANNEL, EVEN IF IF IT"S PROBABLY NOT GOING TO BE A LONG THERM SUBSCRIPTION, IT FELT THAT A PAYMENT HAD TO BE DONE, FOR YOUR EFFORT. About the make a model, well, it"s a french car, that says it all, i think:))) it"s a 2006 Renault Megane 2 with a 1.6 l 16v engine, with some sort of vvt(unilateral, sort of speak, since I think it only adapts the timming of the exhaust). Allthough i realise that this brand is not sold in the US, so I don"t know if that helps more than probably being able to determine to some extent, the world widwe technology limitations of the time the engine was buit, it seemed rude not to answer your question. Nevertheless, i tried to ghether as mouch information about the ignition system and it seems that the french, being french, made it so that the pencil coils are conected in series, or some sort of way that makes them affect one another, like 1 -4 and 2-3(not official info though, and not sure if that"s the right technical slang). I also tried to measure the primary and secondary resistance(for the secondary I could only take measurements between the springs of the coils and one of the two terminals from the coil"s plug and came to find out that no.1 coil had 5 000 secondary resistance(only when warm) when it suposedly should have been between between 9000 and 12000. Primary seemed fine on oll four(it being a four cylinder engine, as i previously said) both warm and cold. Not sure if my measurements were done properly, though, particulary if the secondary can be measured by useing the coil spring as a terminal. However, after seeing another of your "waw" videos on p0300, and how the cranck shaft sensor can determine inconstant spark by a faulty imput and corroborating it with my being unsure of my measurements, AND WITH THE FACT THAT AT SOME RPM RANGE THE BLINKING CHECK ENGINE LIGHT TURNS OFF, it got into my head to try and take it out first ant take a look at it, or even buy a new one. I hate the parts throwing method but i don"t have any tools and no way to get it properly diagnosed at shops(not only becouse of the pandemic but also becouse tecs are to quick to jump at conclussions arround here, wich may turn out to be very expensive). For the moment i cannot do both, coils and cranck sensor, but I can do either one of them. given that you have been so kind I would dare to ask what would you advise at this point.
@@traiansandulescu5051 it sounds like you are describing a standard waste spark ignition coil. When the coil fires, 2 cylinders get spark at the same time. One is on it's compression stroke and the other is on exhaust. 360 degrees later, those two cylinders fire again with the "companion cylinders" swapping positions. The one on exhaust is now on compression and vice versa.
The fact that you said the cylinder drop test was poor on cylinders 1 and 2, tells us it is most likely NOT a coil issue because these two cylinders are not companion cylinders and are on two separate coils. Make sense?
Also, I've found resistance testing to be poor at best. When you get a bad reading, you can typically trust it, but when you get a good reading, it can still be bad as the ohmmeter does not stress the circuit
Genius and a teacher. Thanks
A intake leak will have high short term numbers at idle but normal at 2500 rpm.
A gas analyzer will distinguish between the misfires. Both have high O2 levels
but no HCs on the fuel injector.
P1132 is B1S1 indicates rich (this would cause negative fuel trim numbers. And P1151 is B2S1 indicates lean (this would cause positive fuel trim numbers).
So one bank is running rich the other is running lean, Is it possible the connectors for the upstream O2s can be switched? In other words they are connected to the wrong bank. This can cause this condition. Also you may want to check that thing for a bad headgasket.
Great video, perfect timing. Thank you again!
(continued from previous post) More quick tests are to use a vacuum gauge and checking the fuel pressure. Finally do a compression check and also a Leak Down Test. Too many mechanics out there will only look at the scanner trouble code and just throw parts at it until they finally replace the right one while making the customer pay for all of those mistakes mostly because they don't know what they are doing. Learn how to use all of these tools. (checking spark voltage should be in above comment)
Its Paul btw and thank you.
Fantastic !! Would be nice to see a gas direct injection engine in the shop. Seems a lot of engines are using direct injection and your students will see lots of these out in the field.
Even that isn't 100%. I don't think there is one test that I use more than the other. Cylinder drop test, secondary ignition waveform, primary ignition current ramp, injector voltage and current, noid light, relative compression test with a scope, gas analyzer....heck I'll even use a spray bottle with water in it to find a misfire:)
The one I chose to use will change for what type of system it is and how easy it is do get to the components.
great job man, had a similar disagreement before couldn't win lol... glad you covered this . had a couple question, your using a picoscope right? what model? been looking at some PC based scopes and read some good reviews on the picoscope... any thoughts? and no i cant afford a verus lol as of right now im using a old bench top scope works well and for scanning a snap-on mt2500 and AutoEnginuity proline + Mitchell 5.8 its not the best setup but gets the job done.
thanks, will
- Scanner: Observe ST TRIM & LT TRIM
o Ignition misfire event:
x Most of the air/fuel mixture goes into the exhaust
x Some fuel condenses in the cylinder and enters the oil
→ initial upstream O2S lean reading. STFT rises up to 15%.
x Catalytic converter tries to burn the unburned HC, using up all the O2 from the bad cylinder
→ downstream O2S is 900mV.
I'm following. Keep going! So we are using the downstream O2 as a guide to type of misfire as well. So a no file misfire, the downstream O2 would be flat line lean. No fuel to consume the stored oxygen. Right?
+ScannerDanner during lean misfire event, downstream o2 reads rich due to leftover unburned HC and low o2 (used up by the cat to burn HC). the downstream o2 shouldnt affect fuel trim.
I'm not talking about a lean misfire. I'm talking about a no full misfire.
And to your point. Using this method of viewing the downstream O2 an ignition misfire and a lean misfire would look the same. Making the test not very valuable.
I have found a recent fault in my car involving the Chevy LS1 where I went to fill up with fuel 2 weeks ago,well it involves the check engine symbol appearing on the cluster,the fuel trim being Maxed out to 25% on both banks,the fuel volume tested at about 3 litres per minute,the fuel filter isn't restricted & the fuel pressure tested at 47 psi at the fuel rail.
The conclusion I came to is that the fuel mixture is lean & the fuel pump is noisy due to being worn out,the fuel pressure regulator holds pressure but the pump fails to deliver the 55-60 psi required for the LS1 engine so I ordered a pump to replace that one which I'll do this week.
change your inline fuel filter too if your system has one. Some were built into the pump assembly
great video yet again thank you would love to see some wideband stuff if you had time.
working on it brother
Wrong brand spark plugs will cause a missfire,I see this a lot with Bosch spark plugs installed a lot and seen this with E3s once so far.Ford tritons with the COP ignition system are known for going through coils.Had one Ford in for a missfire showing no codes,had the customer take it to the dealer and it was a bad ECM.Everything else looked good.GM 4.8s,5.3s and 6.0s,spray down the intake gasket area when a missfire code appears.If changes,the intake gaskets are bad,blow out taking in air
Thank you very much
For sure and I have to say that most people think unburned fuel (HC emissions) is rich. It's not.
I have the same exact car. Love my RX!
I thank you for all your wonderful inputs and suggestion. Let me show you the tables of the key parameters and their conditions and they also answer your questions:
After about 8 minutes at IDLE, no speed, RPM = 785, pending codes for misfires all cylinders (P0301-P0306) and P0300 (Random misfire) show up:
1. ECT = 176
2. MAP = 10 inHg
3. Spark advance = 9
4. IAT = 95
5. TPS = 13.3
6. STFT bank 1 = -27.3, bank2 = -2.3
7. LTFT bank 1 = 0, bank 2 = 0
8. A/F ratio sensor 1 bank1 = -0.246 to -0.269mA (before CAT bank 1)
9. Eqv ratio 11 = 0.964 to 0.972
10. A/F ratio sensor 1 bank2 = -0.019 to -.074mA (before CAT bank 2)
11. Eqv ratio 12 = 0.991 to 0.999
12. O2S2B1 = 0.825V (after CAT bank1)
13. O2S2B2 = 0.195 to 0.715V (after CAT bank2)
14. Load = 34.1
Then I drive the car, during ACCELERATION I see O2S2B1 = 0.3 to 0.6V (after CAT bank1)
Per your instruction, I take notes the following numbers during DECELERATION; my foot off the gas pedal:
1. STFT for B1 and B2 = 0
2. LTFT for B1 and B2 = 0
3. A/F ratio sensor 1 bank1 = 3.7 to 4mA (before CAT bank1)
4. Eqv ratio 11 = 1.99
5. A/F ratio sensor 1 bank2 = 3.5 to 4mA (before CAT bank2)
6. Eqv ratio 12 = 1.98
7. O2S2B1 = 0V (after CAT bank1)
8. O2S2B2 = 0V (after CAT bank2)
9. RPM is about 2000
10. MAP = 5.9 inHg
Then about 1/2 hour driving (acceleration and deceleration), I then park the car and let it IDLE:
1. STFT bank1 = -11.7
2. LTFT bank1 = 0
3. STFT bank2 = 0
4. LTFT bank2 = 0
5. A/F ratio sensor 1 bank1 = -0.007 to -0.0085mA (before CAT bank1)
6. Eqv ratio 11 = 0.999 to 1
7. A/F ratio sensor 1 bank2 = -0.019 to -0.070mA (before CAT bank2)
8. O2S2B1 = 0.76V (after CAT bank1)
9. O2S2B2 = 0.2 to 0.7V (after CAT bank2)
10. MAP = 9.7 inHg
11. Spark advance = 8 to 10
12. ECT = 201
13. Load = 32.5
14. RPM = 790
15. IAT = 134
16. TPS = 12.9
Then I turn off the engine and wait for about 10 minutes and start the car again at IDLE:
1. STFT bank1 = -25.7
2. LTFT bank1 = 0
3. STFT bank2 = 0
4. LTFT bank2 = 0
5. A/F ratio sensor 1 bank1 = -0.007mA (before CAT bank1)
6. Eqv ratio 11 = 0.999
7. A/F ratio sensor 1 bank2 = -0.050mA (before CAT bank2)
8. O2S2B1 = 0.6 to 0.825V (after CAT bank1)
9. 02S2B2 = 0.2 to 0.7V (after CAT bank2)
10. MAP = 9.7 inHg
11. TPS = 13.3
12. IAT = 147
13. ECT = 207
Questions:
1. Seems like when I drive, the numbers are getting better until at idle STFT bank1 go back to -25.7? Does 02S2B1 (after CAT bank1) is normal? the 2 A/F ratio sensors (pre CAT) are ok?
2. One more thing, yesterday, at IDLE, I rev the engine to 3000 RPM for sometimes, the P0172 (System too rich bank1) and P0430 (CAT system efficiency below threshold bank2) came up with Engine Light on. I was surprise P0430 for bank2 CAT. Should it be for bank1 instead? Yes, the O2S2B2 values indicated potential CAT problem for bank2, should it be CAT for bank1 instead because of bank1 STFT is too negative - 25.7?
3. Can a restricted CAT bank2 causes STFT bank1 negative?
4. Or the other way around, can STFT bank1 is too negative which can cause restricted CAT bank2 problem?
5. I just order a "smoke machine" which will arrive in next couple of days, will do smoke test in all system. Any other test(s) should I try?
Please advice.
Many thanks & God bless,
Hai
Nice Russ! Thank you
Extremely informative!
Hello your video is very important in the diagnosis of faults. My language is not English. I am using a translator to communicate with you, and have tried to understand what you say , but I do not understand everything. You can tell me the times of the video where behaviors are no fuel misfire and an ignition misfire on both systems please? Thanks.
How would the post cat O2 sensor look in these cases?
Could you diagnose if the misfire is caused by ignition problems or fuel problems by looking at lambda ?
I like all of your upload man
you rock.
great advice thanks!
Honda accord V6 3.0L: Misfires all cylinders sometimes, but STFT = -25% on bank1 ONLY. New spark plugs, new injectors, new PCV, new MAP, new gaskets (intakes, throttle body, EGR, top cover engine), clean throttle body, clean EGR, did valves adjustments, test evap purge valve, new fuel regulator, test coils, very good compression in all cylinders. Still get -25% STFT on bank1 ONLY and sometimes Misfires all cylinders. Any suggestions?
ScannerDanner
15 minutes ago
Okay, that rules out a restricted cat. Next step would be an injector balance test for me.
What year is the honda? Some models will use downstream O2 sensors for fuel trim control, but that is usually accompanied with a wide band AF sensor upstream. If it has downstream fuel trim, we need to focus on the B1S2 and B2S2 sensors.
Of course we need to also focus on the upstream O2 sensors as well. (B1S1 and B2S1). In fact after typing this, that is where I would start. (Testing the upstream O2 O2 sensors)
Hai Ho
1 second ago
@ScannerDanner Good morning ScannerDanner. I thank you for your great inputs. It is 2004 Honda accord V6 with 200K miles. The 2 pre-cat sensors are A/F ratio sensors and I did swap them around and they both are ok; one is new from last year replacement (Amp numbers with equiv. ratio is 0.99 or 1). At idle, After the CAT sensors: bank1 S2 stays high around 0.85 and bank2 S2 does fluctuates from 0.2 to 0.7 and there are times around 0.6V for quite sometimes. I'm questioning this B2S2 for the bank2 CAT however STFT is -25% for bank 1 ONLY. Strange? What is injector balance test? Talking about "balance", the compression numbers for bank1 are 150, 145, 150 and bank2 are 180, 175, 180. Any thoughts?
Hi Paul, very instructive, informative, and insightful video.
After reviewing many of your videos on fuel trims, how would you direct your students to diagnosing fuel trim numbers the opposite of a vacuum leak with an excessive misfire code?
Suppose a 4.6 GM OHV V8 comes in with MIL light for a non-cylinder specific emissions misfire. It has new HT leads, factory plugs, coils, and fuel pressure within specs.
The OBDII scanner confirms the misfire DTC.
Fuel Trim data reveals the following lean condition on both banks.
SHRTF1(%) = +16.4 @ idle to +24.2 on acceleration to 1500-2500 rpm. Drops back down to +12%->+16.4 on deceleration.
SHRTF2(%) = + or - 3 @ idle to +10 on acceleration to 1500-2500. Drops back down to -11% on deceleration settling in close to + or - 3%.
LTFT1(%) stuck @ +16.4 irrespective of driving/load conditions.
LTFT2(%) stuck @ +16.4 as per bank 1.
O2B1S1 oscillating correctly within parameters.
O2B1S2 voltage stuck @ 0.98 -.99v
O2B2S1 oscillating correctly within parameters.
O2B2S2 reading between 0.09 & 0.10v
MAF reads 0.08 g/s @ idle and 0.11 g/s @ 1500 rpm and 0.15 g/s @ 2500 rpm.
Before you say MAF problem, the code reader incorrectly reads the MAF. The correct code reader for this PCM reads 5.1 g/s @ idle for the equivalent 0.08 g/s.
I've cleaned the maf with specific maf cleaner, no out of range maf codes set in PCM.
It appears from your overview that this is a fuel injector related misfire.
But what I find odd is I can't get the Long Term Fuel Trim numbers to move.
Either way, total Fuel Trim numbers trend positively higher on acceleration (opposite of un-metered air leak)but at idle still trimming like a vacuum leak.
ScannerDanner, what's the prognosis?
Many Thanks!
+glycosaminoglycan what year make and model? All I got was 4.6 engine. Also deceleration fuel trim is irrelevant. During deceleration the injectors are shutting down momentarily. The LT may not move anymore because it is maxed out. What do the O2 sensors read at wide open throttle on a test drive? How does it run under load? Do you feel a misfire? Or is it just a misfire code? It may actually be no lean condition at all and the misfire is causing a false lean condition.
+ScannerDanner 1997 Range Rover HSE 4.6 all aluminum Buick-designed pushrod/hydraulic lift with 9.26:1 comp and 107,000 miles.
I just recently purchase a scanner in the last 2 weeks to assist in my diagnosis, I got fatigued going back and fourth to O'reiley's to have the pcm scanned for the MIL light.
I took the engine apart after acquiring it 5 months ago to fix the passenger side head gasket. I rebuilt the top end, shaved .001 of the heads, replaced both head gaskets, new head bolts, valve stem seals, inspected the camshaft for worn lobes, inspected the liners for slippage, cracks and/or corrosion. Engine looked spotless, no sludge anywhere!I Frequent oil changes, but would have benefited from the use of a higher detergent fuel. I had to decarbon the valves and piston crowns.
The fuel injector tips had even varnish discoloration, but none were coated with oil, sludge, or carbon.
Coated every moving engine part with break-in lube, put back together, changed oil, pressure tested the cooling system, started up on a dime! Seemed to run perfect, no valvetrain noise or nasty vibrations, just an illuminated MIL light.
I figured the MIL light would disappear in time, so I drove the rover around town idling in traffic in 113F degree weather since apparently they love to overheat. Nope!
Drove it 60-65mph on the freeway 100 miles in 113F, made it home no problems. MIL light still on.
I was hoping to get the MIL light to flash. No such luck.
I decided since it runs and drives fine, I would disconnect the negative battery terminal to clear the light and take it for emissions.
I didn't know my monitors were not ready, they suggested the freeway for 20 min to get the O2's ready.
Drove the rover 80 mph on the freeway and in 5 min. MIL started blinking and the engine went into 'limp-mode', lost power like it ran out of fuel.
Regained power @ 30 mph, went to O'reilly to get the codes.
P1316 - Excessive Emissions Misfire
P1138 - Oxygen Sensor Engine Rich Bank A
P1171 - Oxygen Sensor System Too Lean Banks A & B
I can't recreate these codes under in-town driving.
I cleared the codes, still getting the P1316 on start-up.
The engine missed and vibrated like the motor mounts were broken before the head gaskets were replaced (cylinder 6 had a break to the outside and into cyl. 4, no oil/coolant passage).
It's night and day now, before and after. I can't tell it's misfiring, no dead spots, or miss in the idle to 3000 rpm rev range, but again I don't how well it is supposed to run.
If you listen to it to the engine run, you would think the MIL light was for evap canister or loose fuel cap.
But the fuel trim numbers are out of whack, so it could in theory operate more efficiently I suppose.
Runs good, perfect idle, no overheating issues (original owner ignored leaking throttle plate heater gasket, simple fix!) but I can't emission it with that MIL light on.
I've researched threads, everyone says plugs/wires/coils, then they replace all 4 O2 sensors and the MAF, then they go after the injectors, then after the dealer replaces everything and the problem remains, they say it's a bad camshaft or it turns out to be a poorly functioning crankshaft sensor lying about random misfires.
I'm stumped.
Thanks for the quick response Paul!
+glycosaminoglycan any chance you plugged in the upstream O2 sensors into the opposite bank connector? I don't like the rich and lean codes on opposite banks. Also I want to know what those fuel trim numbers are doing during the running poorly period of time.
The length of the terminals prohibit switching connections and they are separated by the transmission/drive shaft.
I have to drive the engine near or above 3000 rpm to recreate the limp-mode scenario to throw the misfire/lean codes. I don't know what fuel pressure is at under 3000rpm load traveling 80mph. As of now, driving around doesn't trigger a flashing MIL light.
It is sensing a misfire, but hasn't found which cylinder(s) are the culprit.
It is Bank 1(A) that has downstream O2 reading rich and not switching. Stays at 0.98-0.99v. However the downstream O2 on Bank 2 stays low with an occasional switch to .98 then back to 0.08 then to 0.46v then back down ~0.10v before jumping back up to 0.98v and returning low again.
SHRTFT1 is very responsive to throttle response. Easy to go from +15 to +21.4.
SHRTFT2 finds 0 occasionally at steady throttle 1500rpms.
LTFT 1&2 haven't changed at all, stuck at +16.4.
Load % seems high at idle ~28-30%
Moves to 49% on acceleration.
Getting horrible gas mileage at idle, burned through a 1/4 tank just idling 30-40 min.
Before throwing the 3 codes on the highway, MPG's were excellent as I put over 100+ miles on it during that time.
I will say that I unplugged the MAF @ idle and instead of running poorly, it came alive like it had full power again but with an accompanying increase in idle rpms.
I also pulled the fuel regulator vacuum hose and recorded a corresponding increase in fuel pressure of approximately 8psi. Did not run any better or reduce the high positive trim numbers.
I did plug the vacuum port to the intake after disconnecting the fuel regulator hose to prevent a vacuum leak that would skew the trim readings.
What would cause a negative short term fuel trim with cylinder misfire? Fuel leaking into crankcase/PCV system (high pressure fuel pump seal bad)? Vacuum leak? Bad sensor? Poor compression? Carbon build up on intake (GDI engine). The engine also has run-on after shut off. 2013 Equinox 2.4L
Everything you mentioned except a vacuum leak would be possible. Typically when you see negative trim numbers with a misfire it is from a mechanical issues
@@ScannerDanner Thanks for the feedback. I will check compression over the weekend. The LTFT was -20 to -40 also. Eco-crap engine! Intermittent P0303 code, but no P0172 code. Time to scrap or put in a new engine. Probably timing chain and water pump weren't far behind. No more GM products in my future.
@@mjkirk12 focus on that injector with it being GDI and that negative of trim numbers!
@@ScannerDanner It was a mechanical issue - a leaking high pressure fuel pump - replaced and now the STFT and LTFT are back in normal range. O2 sensors good - front toggling, rear smooth. I guess the fuel pump is known issue with the Ecotec 2.4L Fuel vapor from the leaking pump pulled into intake via PCV causing rich condition. The P0172 code was stored (last week) along with the misfire P0303. Compression on cylinder 3 was good (similar to the others). With new fuel pump - no more engine run-on (dieseling) after shutoff and smooth idle as well. Changed the engine oil and filter as there likely was fuel in the crankcase oil.
I have watched several of you videos and they are Excellent. At the last part of this video I see that the LTFT was high and the STFT went to 0 as it went into Open Loop. As expected when an electrical open on an injector. What was not clarified is even if in Open Loop the LTFT are applied to the fuel calculations. STFT is not used but LTFT is? I have proven this to be the case on older Fords just not sure if it is across all brands.
I would answer and say yes and no. I've definitely seen the LTFT numbers being applied in an open loop situation, but on others not
@@ScannerDanner Thanks that is what I thought too.
I see the adaptive update table in most of the pre 2004 ford calibrations only allow the PCM to learn in cruising engine loads and RPMs cells where Closed loop would normally take place. What is learned in these cells of the table are then applied to other Loads and RPM cells. Ford Realized this and made cells that were in the Open Loop ranges point to cells that were in the Closed Loop Area. It makes good senses if a MAF is dirty and the reading is incorrect that it would read incorrect in all ranges not just closed loop.
Keep up the good work on the Videos
@@clintgarrity2693 I had a dodge truck, full size, mid 2000s maybe? Had a bad upstream O2 that maxed out the fuel trim (both ST and LT) and I don't remember the specifics but LT was a factor right at start up on a warm engine. So before it went back into closed loop, there were immediate fuelling issues and poor running
@@ScannerDanner good to know
sorry, I will make sure to not do that next time. that is good advice
Good job, ScannerDanner!!!
Dear Paull,
As I was "smoking out" for any leak from the top of the engine, I saw smokes from the EGR valve (inside the EGR body, not the contact part to the intake). This is for my 2004 Honda accord V6 3.0L engine. What is the relation of such leak to the fuel trim for this MAP based Honda engine? Regular MAF based engine, we should see positive STFT, right? But for MAP based engine, the STFT will be negative, right? Should I buy a new EGR from Honda or the aftermarket?
Many thanks & God bless,
Hai
And I need to improve my knowledge ...thanks
Excellent information.
I stopped watching the video about 5 min into it I watched a fuel trim explanation video on a channel called Schrödinger's box (geared more to diy's who still use critical thinking instead of parts changing) and he PROVED that you can distinguish between spark related vs fuel/air mix related misfires check it out p.s. its not me
What about using pre and post cat O2 sensor data? I've read a bit on that and ( even though I haven't personally tried it yet ) it seems like a very good way of pinpointing what type of misfire you've got.
For sure, I've since learned those procedures as well. Thank you! I'll do a video on it sometime.
You have to learn new things? I thought you were born with a silver multimeter in your hand :-) Seriously though, I found a nice case study on AES using this technique and a nice article from Motor magazine that might help someone:
resources.aeswave.com/ATG-02-Advanced-Drivability-Diagnostic-Strategies.pdf
www.motor.com/wp-content/uploads/Shots-in-the-Dark-Engine-Misfire-Diagnosis-Nov-2006.pdf
thank you for the information ,,great book I love it
Buena presentación.
Excellent.
I had just purchased a Bosch 2220 and was struggling to understand the information especially about short term fuel trim but your explanation convinced me that I have an issue with inlet manifold at idle
subaru impreza wax DTC P0171, RPM 740 , STFT 25 and LTFT 14.8 , MAP36.0 . MAF 2.1 . g/s . oxygen sensor 3.943 V if engine RPM 3000 STFT 2.3 LTFT 14.8 what is causing it ? thank you Danner ,
Dear ScannerDanner, here is the "full picture" of the Negative fuel trim problem (STFT = -27) only on Bank1 for my car, please HELP, please:
2004 Honda Accord 3.0L V6 Engine LX model: (about 200K miles)
After about 8 minutes at IDLE, no speed, RPM = 785, pending codes for misfires all cylinders (P0301-P0306) and P0300 (Random misfire) show up:
1. ECT = 176
2. MAP = 10 inHg
3. Spark advance = 9
4. IAT = 95
5. TPS = 13.3
6. STFT bank 1 = -27.3, bank2 = -2.3
7. LTFT bank 1 = 0, bank 2 = 0
8. A/F ratio sensor 1 bank1 = -0.246 to -0.269mA (before CAT bank 1)
9. Eqv ratio 11 = 0.964 to 0.972
10. A/F ratio sensor 1 bank2 = -0.019 to -.074mA (before CAT bank 2)
11. Eqv ratio 12 = 0.991 to 0.999
12. O2S2B1 = 0.825V (after CAT bank1)
13. O2S2B2 = 0.195 to 0.715V (after CAT bank2)
14. Load = 34.1
Then I drive the car, during ACCELERATION, I see O2S2B1 = 0.3 to 0.6V (after CAT bank1)
Per your instruction, I take notes the following numbers during DECELERATION; my foot off the gas pedal:
1. STFT for B1 and B2 = 0
2. LTFT for B1 and B2 = 0
3. A/F ratio sensor 1 bank1 = 3.7 to 4mA (before CAT bank1)
4. Eqv ratio 11 = 1.99
5. A/F ratio sensor 1 bank2 = 3.5 to 4mA (before CAT bank2)
6. Eqv ratio 12 = 1.98
7. O2S2B1 = 0V (after CAT bank1)
8. O2S2B2 = 0V (after CAT bank2)
9. RPM is about 2000
10. MAP = 5.9 inHg
Then about 1/2 hour driving (acceleration and deceleration), I then park the car and let it IDLE:
1. STFT bank1 = -11.7
2. LTFT bank1 = 0
3. STFT bank2 = 0
4. LTFT bank2 = 0
5. A/F ratio sensor 1 bank1 = -0.007 to -0.0085mA (before CAT bank1)
6. Eqv ratio 11 = 0.999 to 1
7. A/F ratio sensor 1 bank2 = -0.019 to -0.070mA (before CAT bank2)
8. Eqv ratio 12 = 0.996 to 0.999
9. O2S2B1 = 0.76V (after CAT bank1)
10. O2S2B2 = 0.2 to 0.7V (after CAT bank2)
11. MAP = 9.7 inHg
12. Spark advance = 8 to 10
13. ECT = 201
14. Load = 32.5
15. RPM = 790
16. IAT = 134
17. TPS = 12.9
Then I turn off the engine and wait for about 10 minutes and start the car again at IDLE:
1. STFT bank1 = -25.7
2. LTFT bank1 = 0
3. STFT bank2 = 0
4. LTFT bank2 = 0
5. A/F ratio sensor 1 bank1 = -0.007mA (before CAT bank1)
6. Eqv ratio 11 = 0.999
7. A/F ratio sensor 1 bank2 = -0.050mA (before CAT bank2)
8. Eqv ratio 12 = 0.99
9. O2S2B1 = 0.6 to 0.825V (after CAT bank1)
10. 02S2B2 = 0.2 to 0.7V (after CAT bank2)
11. MAP = 9.7 inHg
12. TPS = 13.3
13. IAT = 147
14. ECT = 207
Questions:
1. Seems like when I drive, the numbers are getting better until at idle STFT bank1 go back to -25.7? Does 02S2B1 (after CAT bank1) is normal? the 2 A/F ratio sensors (pre CAT) are ok?
2. One more thing, yesterday, at IDLE, I rev the engine to 3000 RPM for sometimes, the P0172 (System too rich bank1) and P0430 (CAT system efficiency below threshold bank2) came up with Engine Light on. I was surprise P0430 for bank2 CAT. Should it be for bank1 instead? Yes, the O2S2B2 values indicated potential CAT problem for bank2, should it be CAT for bank1 instead because of bank1 STFT is too negative - 25.7?
3. Can a restricted CAT bank2 causes STFT bank1 negative?
4. Or the other way around, can STFT bank1 is too negative which can cause restricted CAT bank2 problem?
5. I just order a "smoke machine" which will arrive in next couple of days, will do smoke test in all system. Any other test(s) should I try?
Have Done:
1. New PCV (Honda part)
2. New Gaskets (Honda parts); EGR, Throttle Body, Intake, Valve Cover, Spark Plug tubes
3. New Injectors (Aftermarket; Standard InterMotor)
4. New Spark Plugs (Aftermarket; Denso)
5. Whole Fuel Unit (Honda part); regulator, filter, pump ...
6. New MAP (Honda part)
7. Clean EGR.
8. Clean Throttle Body
9. Clean EGR path from Intake
10. Did Valves Adjustments
11. Did Static Compression check: B1 (152, 145, 150) and B2 (185, 175, 185)
12. Tested EVAP Purge Valve
13. Drop out test
14. Tested Coil and Spark Plug together for sparks
15. Vaccum measurement at Idle = 19 inHg, needle is stable
16. Fuel pressure = 58psi
17. After installed new injectors, when new injectors in the fuel rails exposed, turn on key and see fuel pressure is at 58psi stable, no leak injectors
18. Water test for leaks. Result = no visible problem.
Will further tests:
1. O2S2B1 (disconnect and see how this effect STFT B1 ?)
2. Swap O2S2B1 and O2S2B2 (make sure O2S2B1 is ok ?)
3. Disconnect CAT bank2 or both CATs to see its effect of STFT B1 ?)
4. Injectors Balance test ... need Honda instrument/fitting/Gauge and bi-directional scanner for this test ?
5. Smoke test.
Yes. The vast majority of stuff on the road today is metric. It would be smart to get all your metric stuff now before you worry about SAE.
Dan, I have a 2001 5.3 tahoe with a code p0300 code. Borrowed my buddies scan tool. Misfire starts only when engine reaches operating temp. I noticed my o2 sensor B1 STFT trim was -31.2. MAP reading is 12.6. Fuel pressure is normal. I just started diagnosing my problem. All emmision sensors are new. I can run live data with this tool. What are normal readings for this engine at normal operating temperature? Any advice would be greatly appreciated.
thanks,
Tony
@ScannerDanner Thank for the video. Could you help me make sense of these STFT and LTFT values. I have 07 ford taurus, for bank 1 STFT stays between +/-3%, but LTFT stays constant at about -12% at Idle. Bank 2 is lean at idle with +12% total fuel trim. When I increase RPM to 2500, STFT jumps between +/-6% and LTFT stays constant at -19%. Bank 2 improves at 2500 RPM with about +6% total fuel trim. OBD says cylinder 1,2, and 6 misfire. I have tested injectors, replaced the leaking injector already. What do these trim value mean? How come bank 1 is rich and bank 2 is lean? Thank you.
not sure if i understand this.. both trims read lean because o2 sensor job is not to read the extra fuel, they read oxygen, and there is extra oxygen both conditions.
no fuel or no spark o2 sensor will detect xtra oxygen? help here!!
Nice video bro
First of all ,an excellent presentation.My car is running rich with O2 sensor 1 reads from 0.45 and shoots up to 1.2 v as engine starts.Could it be lack of compression on one of cylinder which cause rich on O2 sensor 1 .
I'm confused, in your LT ST basic overview you where saying you can Identify the part causing the problems with LT and ST, be it injectors or pump. But in this video your saying it more or less is worthless for detecting a misfire. Are you saying that if you can get to the point where you know it's lean then LT and ST can be useful? Can this be used for cars with no schrader on the rail and are a pain to test fuel pressure?
I'm lazy. I like to cut-and-paste hyperlinks. You have two hyperlinks listed in your videos that are shown only when annotations are enabled. I wish that you had these hyperlinks under your video description so that lazy persons like me can cut-and-paste them.
Hi Mr. Scanner? Could you kindly enlighten me on where the fuel trims feedback fetch from? is it from the oxygen sensors? I recently had a scenario where P0200 was stored in a Toyota Rav4 with 2AZ fse engine and vehicle wouldn't rev up and it will stall but by disconnecting the oxygen sensors it would behave well. This is where i noticed that even with the oxygen sensors disconnected the fuel trims were reading rich! so my quetion is other than oxygen sensors is there anywhere else the ECU reads fuel trims from?
Thanks.
Kingstone Joseph i have the same car and having some issues on it if i disconnect my 02 sensor no code or any feed back comes up even in a scanner while connector disconnected no codes and no diff in engine behaviour
excellent video. not sure if anyone will read this but wanted to know if fuel trims can effciently help diagnose misfires issues. I have a V6. CHECK ENG Light P0300 and P0302. LTFT reads -6.3% on bank 1; nothing alarming when I increase RPM to 2500. LTFT remains -6.3%. LTFT &STFT bank 2 very close to 0%.
Very confused here.
Note: engine just rebuilt and Cylinder 2 piston's had a hole in it before being rebuilt.
spark plugs are new, Ignition coils was replaced.
Personally I think Compression test on Cylinder 2 should be the first step in a process of elimination.
Any inputs? please chime in. this is for a 2009 chevy traverse 3.6L/ Thanks
the minus fuel trim % is suggesting that your problem is not an ignition misfire or a no fuel misfire. If you have a constant misfire on the #2 cylinder, then yes, I agree, check compression next. This would be a good video for you to watch.
ruclips.net/video/uB9XCDO8oa8/видео.html&lc=UgzeS0VThWMchtJ32b94AaABAg
thanks for your prompt response. I will watch it immediately.
Another question for you. this one regards the proper procedure for a compression test.
I like to do everything by the book; according to repair manual all spark plugs must be removed, ignition disabled, floor the gas pedal and crank 6-10 times. No compression under 140psi for the 3.6L traverse and no more than 25psi difference between highest and lowest compression (sorry to have to write all this)
The mechanic who just rebuilt this engine states that compression can be checked by removing one spark plug only.
What is your opinion on that?
IF U FEEL THE ENGINE VIBRATING ESPICALLLY WHEN U PUT ALOAD ON IT LIKE COMPRESSOR JUST DO BASIC SPARK AND FUEL I BELIEVE TO MUCH IS SCANNER DATA LOVE U CHANNEL
Not what we are trying to do here. It's about learning your equipment and using ALL the tools that are available to you
@@ScannerDanner yeah but if the equipment is not helping you by giving you trims and short and long then the equipment that you're using you're just wasting analysis or nothing if I need to use a scope but I use a multimeter instead for a microprocessor I'm wasting my time looking at data outputs and logic outputs that's where we disagree
@@ScannerDanner and I also feel that people are too much reliant on a scanner to do everything for them nobody opens up a wiring diagram anymore and I understand obviously it's electronics I'm in electronics but still they're relying on the scanner to tell you every single thing when some of this the problems is basic electronics we disagree on that
@@Joeelectronicschematicsforauto in no way is looking at scan data and knowing how to use it a waste of time. I literally just used fuel trim numbers to ID which bank on a 92 Corvette had a misfire. In these years there are no misfire counters and this was a GREAT guide for where I was going before ever leaving the drivers seat or even opening the hood.
I dont understand your argument against learning these techniques. Learning to use ALL of the tools in your diagnostic toolbox is absolutely important
@@ScannerDanner I understand but I'm saying sometimes it's Overkill to use a scan tool all the time and not go to basic electronics of a schematic
Another brilliant vide.. By the way how can I buy you book and ow much dose it cost, Currently I am studen
WELL OK BUT
What could Possibly make a car run NEGATIVE then ?