Engine Misfire Under Load - Diagnosing And Troubleshooting One Of The Most Common Drivability Issues
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- Опубликовано: 7 сен 2024
- You've got an engine that idles perfectly and drives down the road smoothly with no noticeable issues, but when you hit the gas hard, the engine drops out. It stutters, bucks and pulls back.
Classic load induced misfire. It's a common problem with simple solutions. But, if you don't know where to look and what it is you're looking at, you can pull your hair out trying to fix it.
Here's an overview that covers the basic diagnosis, common causes and simple fixes for the vast majority of load induced misfire problems.
#classiccars #musclecar #engine
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"...the shop is in utter complete chaos"
[One of the quietest, cleanest garages I've ever seen]
Yes, I agree with you!
Exactly correct. My 87 W150 would start misfiring under a load, especially when towing. I mentioned it to a friend who told me to do a "midnight test" on it. So I did. Went out after dark, started the truck and revved it a little and found sparks flying everywhere. Distributor cap, at the plugs, even one plug wire had a bad spot in the middle. Tune up completed next day, problem fixed.🙂
Especially in highly humid conditions, such as a rainy day. You can lighly spritz your plug wires (one at a time) with water mist if you suspect one is bad. Wetting a marginal wire will expose damaged insulation issues.
And don't buy the cheap generic stuff either. Mallory wires work well for years.
I never tried them (Mallory wires) but will give them a shot.
It also helps it you spray water on the wires with a squirt bottle.
Man I'd love to have a father like you to teach me the ropes of these old hot rods. Ive always been into cars. But I've been self taught ever since my grandpa passed away. You remind me of him very much. My father was never in the picture. So I relied upon gramps to teach me the way.
You'll just have to do your best and be a father for some other young mechanic one day.
@@OlMrEllis Amen! It's important to pass along such knowledge but only if they have an interest in it.
@@OlMrEllis amen! Good thoughts and comment!
Use the force Luke.
@Remington Steel Who isn't old enough to be a father? Tony?
Surely you're trying to flatter him.
Tony, not being critical. Just a reminder. As you say, "With the engine running pull the coil wire..." For the novices out there that may think the coil and plug wires are well sheathed and insulated and you won't get shocked, WRONG! Make certain your hand is insulated via a heavy rubber glove or preferably pull and replace the wire with an insulated pliers. Good content as usual, Tony.
I have been booted even with 1000v vde electrical pliers... But only when pulling the leads off the plug end. You are safe to pull them from the distributor end
Mechanics get shocked by that repeatedly, and It's no big deal. You hate when it happens, but immediately keep on doing it. I'd worry if i saw my mechanic donning rubber gloves over that.
My first thought when he said to pull the coil wire is somebody is going to get knocked on their butt and cuss him out for sure!
@@izaacbanks3337 One way of checking that there is spark. Like testing a condensor; put it across a battery and throw it to someone to catch. If they jump it's good - if they don't jump replace it.
Shock and pain is how you learn "don't do it that way". Smart people learn the first time. Stupid people it takes about 10 times or so. Took me about 200. Even if you are as stupid as me, eventually you learn because pain sucks.
I used to have a great boiler service tech. The guy was a friggin wizard. He’d always tell me “ look for the simple shit first!”
Yup I'd say that works for me 3/4 of the time, especially for work there's no time for the rabbit hole.
Sling Blade. "Ain't got no gas."
I had one of those super coils on a mustang back in the nineties. I didn't have room to mount it standing up, so I mounted it on it's side. Every I ran it long enough to get up to temp, it would push a little oil past the O-ring between the top and bottom of the case. Finally it pushed enough out to make the coil fail. It started out misfiring at about 6200 rpm, and got bad enough that I didn't think I was going to make it home. I didn't see the oil leaking, because I kept it so clean that the leak didn't have a chance to show up. I only noticed it when I pulled the coil and there was oil in the seam,and a single drop hanging on the bottom. I pulled the top off,and there wasn't a table spoon of oil left in it.
Please keep these tech tip style videos coming. Im a vintage auto mechanic and I love these videos. Just had a customer the other day that had this exact issue.
The best old school car channel on youtube, plain and simple. UT's knowledge will help to keep classic cars running for decades to come.
This is really good! In case anyone is wondering how it's possible that a wider gap can "amplify" the spark, I think what's happening is the coil is not allowed to release its energy until the voltage rises to a higher peak, which ends up with a more violent spark at the cost of a small added delay.
that’s exactly it, the coil builds its voltage until the spark jumps the gap. larger gap demands a higher voltage which creates a hotter spark up to the limit of the coil
Years ago on my 1977 360mopar I had just rebuilt, new cap/rotor, new plugs & wires it would shoot a flame out of the carb about a foot or so only when driving under load, after driving me nuts for hours & checking everything over and over it turned out to be a bad plug wire going to number 1 which I didn't think being brand new would be the cause.. I finally decided to change the plug wire one by one and as soon as I changed #1 plug wire the problem was gone.
I learned an important lesson last month on a "misfiring" issue only at low Rpms.
Always check both ends of the plug wire before you start changing anything.
I changed plugs, went to the junk yard and got several different sensors, a set of fuel injectors..
Lol i hate to admit this but i never pulled the plug wires off the coil side, only looked at the plug sides.
Ended up being one of the connectors got water in there and rusted on the wire coil side..
I always say look at the simple easy things first..and then there i go with the parts canon😄
Thank you for helping me look in the right direction for my 55 Thunderbird misfiring underload problem.
Now you got me motivated to replace the sparky bits on the truck now to get O'Reilly to come up with eight R44TX spark plugs at one store. Okay Fife has one, auburn has four. 324th store has two . Used to be a common plug.. even going for a new cap and rotor, one of those fancy red ones even new wires. It's been a while since I changed those .. the fun part of the whole thing is getting My stroked out oldass up into the engine compartment of the lifted square body truck. Everything else is easy with one functional hand, it's just getting to it.
Totally normal for those stores, I was at auburn south to get plugs for my geo metro last week, 3 cylinder engine and they only had 2 plugs 😂
Hang tough, mud duck!
Recently had this symptom with my c10 and had to figure it out for myself. This video may not help me now but it will sure help others :)
I have been subscribed for years but haven't needed the "learn'in" for a while. But this week I have been dealing with backfiring under load. I followed your logical explanations, tracked down the problem (one of the SP wires was not tightly clipped to the plug), fired the car up and was driving like it was supposed to in less than 30 minutes. I'm happy again without using the new parts cannon. Thanks for the help.
73 coronet was my first car. and im only 27 today. mine was an old cop car. love the videos!
Best practical information channel on youtube. Never stop
Thank you for this video!! Ive been chasing this exact misfire for too long. Threw new coil packs at it with no improvement... watched your video and discovered my #4 plug wire wasnt on my plug! Pushed it on there snug and now the misfire is 98% gone. Time to replace wires 😅
I've been recycling 1980s Ford Racing 8mm wires on me 1986 5.0. Amazingly, those wires ohm out fine and even on all 8 wires, with tiny variations for length. They didn't build stuff like crap as much back then. I've tested *new* wires from today that fail an ohm test out of the box.
A tremendous source of automotive knowledge and wisdom. I especially love these types of videos, instruction from years of experience. I'm truly appreciative, hands-down, the absolute best channel on RUclips...
Let’s share these videos and get Tony to 300,000 subscribers
Tony...as an Electrical/ Electronic Troubleshooter for many years who Prided himself on Never taking the Shotgun approach to Troubleshooting I find myself doing just that as I get older!? I have a 1994 Ford F150 that has developed a Missfire. I Changed the Plugs. I Changed the Wires. I Changed the Cap. I Changed the Rotor.
It still Misses!!! Next the Injectors I guess.
Man we learning some stuff now , got to check all this stuff, got a 318 I put a rebuild carb on , idles good runs good , you step on it and it coughs and then goes
Been chasing a random loss of ignition issue with my HEI distributor. It was as if someone would reach over and shut the key off. First, replaced the module, helped but still died here and there. Turned out to be the coil in the cap. Also found the base of the chinese dizzy to be cracked, so replaced it with an old AC Delco unit i found at the junkyard and rebuilt. Somehow managed to eyeball perfect 6° timing, but i couldn't leave it alone and tweaked it to 8°. It ran pretty good. Next time i drove it, after a while i noticed it has a very slight intermittent bog at 55mph. It then died shortly after i noticed. However, it immediately fired back up and ran fine for another half hour, at 45mph the most. Anything higher it began to bog occasionally (thing revs pretty high). I get it to my shop and correct the timing to 6°, but now any time there is any load, it misfires badly. It is definitely spark where it is so load based and such an abrupt loss of power. Anyways, i had pulled the new cap off and noticed a lot of carbon where the button is supposed to meet. The button looks like it was making contact, but i could be wrong. Will bend that prong up some and see if that makes a difference.
Thx Tony and great misfire/ stumble sound effects
I had a hair-pulling experience with this on a 3rd-gen RX-7. It ran fine until it built boost under load, when it would start surging until you lifted the throttle. I left it at a Mazda shop (not a dealer) for two or three months so they could swap parts on it. The last thing they tried was the coil packs. One of the coil packs and a cable were bad. I threw about $500 dollars in parts at it just prior.
12:50 and the gap from the rotor to the cap.
bingo.. amazing he overlooked that; no gap, no spark, not to mention contact welding.
And I most certainly got something out of that.
Tall coil plug tower potential problem area noted
I have always used a lubricant when installing new wires, especially at the cap. My go to was WD40. Wet the wire, asd and pull back the boot, install the metal until it bottoms out, and then seat the boot fully.
I'm such a well grounded fella I got shocked just looking at this video.....
Love the sound effects related to the misfire and fuel related stumbling issues Tony.
Perfect timing ! Lol
My 87 GTA has been developping misfires under load and now it's really unpleasant to drive at anything but cruising speeds with a few misfires here and there. The wiring and spark plugs look good and had been replaced not so long before I got the car, but with aftermarket stuff you never know the reliability. I'll check all that as soon as I get home.
Tony, I finished this video and went straight out to the garage and checked my coil, distributor and plugs. I've been troubleshooting abrupt stumble on a 360 and was about to fire the parts cannon. Thanks for inspiring all of us out there to double check the little stuff that makes a huge difference!
I want to see this parts cannon everyone is talking about!
Good Timing on this Video, i am having that problem Right Now, will be checking all you just said tomorrow.
Thank you for this video! Now, I do not feel so weird for being picky about putting plug wires back on to spark plugs and into/on to coils and distributors! I literally had people give me grief for taking my time to make sure plug wires click into place, and are not just sitting there.
Had vandalism. Plug wire pulled off, connecting clip Removed from interior of boot and put back in place. Everything looked normal.
Sinister.
Would love more secure boot clip connectors.
@@MPRiley-rb6lj heh, I changed the wires on my vr6 the other night ,and I needed a big wide straight screwdriver and all my weight pushing on the top of the connector to hear and feel that click onto the plug end.
There was no way you'd push em on by hand , even better would have been a slotted piece of pipe to spread the load but I didn't damage them.
Damn things were wicked, I'm not worried about one coming loose!
I get what you're saying about misfires. However the issue I have with what you said is a "misfire" is labeled by the pcm in modern cars as anything that doesn't produce thrust onto the crankshaft.
Well, he is correct, the PCM does not see the CKP signal in the expected time, and that is because the crankshaft was not accelerated by a power pulse, that is 100% correct, and with a proper functioning cam sensor, the PCM "knows" which cylinder isn't firing. Industry standard in 1996 with the advent of OBDII...
at the spark plug and rotor to cap... I couldn't resist. lol I gave you a thumbs up anyway
I like your explanation between 'misfire' and 'hesitation'. Exception! I once had a vehicle that sure felt like a fuel problem. I chased fuel and carburetor for some time. What I finally found was a weak condenser. It acted like a bad accelerator pump or power valve issue so close.
Btw, great video. The one regarding brake hoses was helpful too. Cheers.
Had an issue on my 85 d150. At high rpm only under load it would just die until rpms came back down to 3000 rpm or so. Turned out to be the ignition ecu going out. Not too bad for a 38 year old part. New one has lasted 2 years just about now which i think is pretty good for a chinese unit. Still have the old faulty oem box in the truck just in case this one fails so i can limp it back.
Spraying water on the coil will normally show the cracks also make it run like crap. I always kept a squirt bottle on my tool box, over night condensation builds up under the hood and can cause all kinds of weird problems the customer complains about that you can't replicate on a warm day. Found many ignition problems just misting down the ignition system, bad grounds cracked caps, bad wires. My 2 cents.
Your distributor cap demonstration answers a lot of questions with a misfire I had years ago with my 5.9 magnum. Right on Thank you Uncle Tony 👍
I LOVE your channel/perspective. It def comes from experience and living in the real world! I went to tech school and they push ideal situations, then I worked as a tech in a full service corner gas station in a small town. And some dealerships. And of course 45 years of DIY for myself/friends. I love your 'plugs are gapped about right"...yep! Don't need to be perfect!
Great topic Tony, it's Remedial Math, for old car people. I hated Remedial school topics when I was in school as a kid. Though now, I'm much older, and that father and own uncle Joe, (my God father), have passed away, it's so important, to keep passing these lessons onto our "Village".. I was mesmerized watching you give this "Campfire" story to us kids . Keep these types of topics coming.. They'll only make us better at our hobby. God bless..
@uncletony I wish you did this story about a year ago! I literally just solved this problem with my truck over the weekend! Very valuable information your giving out!
Man, I appreciate this video. I've been walking through some really weird drivability with my car, so looking at rods and come up springs for my Edelbrock on my 429 Galaxie (thanks for that video btw), and while I was testing, i got exactly the symptoms you explain for igitiion. Vacuum advance diaphram was disintegrated. Saved me days worth of work. I'd already checked the cap points and rotor.
A misfire caused by a slightly lean accelerator pump setting does not hit softly, it has the exact same symptoms as an ignition misfire with the engine sounding like someone dumped a bucket of water on your distributor cap during hard acceleration causing crackling and the ignition breaking up. A lean misfire can be very hard to diagnose because it sounds so much like an ignition problem when in fact it is a carb problem. I chased this problem for months changing out ignition parts and finally fixed it by upping accelerator pump squirter size.
Well it was great you did this video as it has refreshed me on why my car might be runninig badly. Thanks for postinig good solid info.
been watching from day one! Always learning ! Sometimes just common sense Where did that go? cheers Crazy Botts! ps i have the t shirt lol
I had a cap that was bad that looked absolutely normal. The spring loaded center pin of the cap would get stuck in sometimes. Drove me crazy. Now, I always check to make sure it moves freely.
4:37 Weak spark could also be due to bad/pitted/burned points or bad points-coil wiring.
Make points great again! Points are alive and well in aviation engines to this day
And magnetos are neato
"Points" - don't ever want to hear that word again.
I must say your videos are a Godsend on days! Helps me diagnose stuff quick and easy! Thank you sir!
I got a different problem but this still helps. Its on an old 4banger '81 toyota truck tho. This thing runs better under load. Empty it starts chugging(soft onset! I learned something!) Load it up with firewood, go up hill, and it runs great!..maybe not that big of a problem
I had that problem once and the engine was twisting on the mounts enough to pull on the distributor power wire to give it a shoddy connection, damnedest thing. The little plastic tab on the distributor that the arm on the connector is supposed to hook over was worn down enough to let it back out a bit
So much practical knowledge. It’s great to see Tony. Where were you 40-50 years ago when my dad was struggling in the driveway… Ha ha.
Great video as allways great information/knowledge I really learned from this video as iam having a problem with my olds 350 with a quadrajet on it upgraded my coil but will check the voltage on the coil iam having a slight misfire while idle but when under load it’s not as bad definitely goin to do and check these methods thank you uncle Tony allways helpful 👍👍
Hey Uncle Tony! How bout a video on GM HEI units? I’ve got a nova that runs great, but once she gets warm starts having stall issues at low/idle RPMs. No problems under load.
Quite so. Love you, UTG. My 1994 Suburban... misfires. New wires, cap, rotor. Just revving the motor in park told me nothing. I put the thing in drive (auto trans) parking brake on, chocked the wheels and waited for darkness. I revved the motor by hand (TB) in the darkness. Nothing. Then I filled a spray bottle with water. I sprayed the sparking plug wires and got a lightshow. My wires were new (I will not disclose who made them... COUGH AC COUGH DELCO) and they were blowing sparks everywhere.
I went to a different brand of wires and never had another problem with my wires.
Thanks man. I've returned so many "new" parts this year alone. What is going on? Had a 1 month old spark plug die on me. Full weekend to find the problem as I thought it's new so I don't have to check that. My 3 month old steering rack is already clicking - can't send that one back. Multiple other stuff breaking or just failing 1 to 6 months after use. - all brand new.
As the cylinder pressure increases, more voltage is required to jump the plug gap. As the coil voltage builds (because the spark event has not occurred yet), there's more chance of the energy jumping over to ground (and not across the plug gap) as the voltage increases. Current will always take the shortest path to ground.
Ill never forget my grandfather showing me how to pull wires and check spark. I was sitting on the fan shroud of a 1988 GMC when I reached over to pull the coil wire and shocked the piss out of myself lol truck died instantly and my grandpa jumped out wandering what had happened 😂 lesson learned that day
lol
Just watched the video decided to watch spark it was missing bad at 2k rpm cutting spark so i replaced hei module in my dodge 360 and it fixed my issue
Another cause of hard-starting, misfiring, and lack of power is: Coil Wire and/or Plug Wire Resistance. It will also appear as a weak, orange spark. Tried to chase the problem for days until I took resistance readings on the Coil and Plug wires and every day the resistance would increase 1000 ohms or so. But the wires looked fine! Found a NAPA store that would sell me a coil wire, not a full set. Installed it and car ran better. Then installed a full set of wires and performance was back to normal.
Again, the wire set, Packard 440s, looked great, but they were 25 years old !!
I had a similar issue with a '64 Chevy with a straight 6. When the engine was cold it would run great. When it got hot it would run like crap after a while. Turned out it was the coil. When it was cold it was fine. When it got hot it woul;d not work well. With the heat the insulation would fail. It took a while to figure that one out.
Great advice and often overlooked or misdiagnosed. Love ya work. You're a Champion and that doesn't mean your head is shaped like a spark plug.
Never assume there is only one problem.
One booger of a diagnosis for me ultimately turned out to be a missing tit which was supposed to retain the distributor reluctor coil. This allowed the coil to rock back and forth which cracked the insulation on the wires. The wires would short at certain RPMs. Also the fuel pump pushrod would bind in the bore and float on the cam when the engine reached operating temperature.
Having two or more distinct intermittent issues makes for a challenging repair.
Hey Tony, I have also found this misfire issue with spark plugs, where they have carbon tracking, and you can actually see the spark plugs glowing and flashing right through the ceramic in the dark when the engine is under load.
Old ignitions sucked my dad told me to push the wire out of the boot then push them in until the clicked then push the boot down then turn off the light and brake torque it and look for arcs jumping. Old wires were not good from the start. I still have wires hanging in my garage in case one goes bad even though that doesn't really happen anymore. My 92 chevy truck used to have build-up on the inside contacts on the cap and would missfire when it got cold out. I got the expensive copper cap but it still did it. I don't miss caps and rotors until a cylinder coil goes bad for $120 a pop.
98 chevy 454... I'm starting with the silly spider cap on the distributor, and rotor. I'll ohm it out, testing for shorts because the cap desigh is silly, and destination is "It'll fail cuz it's silly".
One of the best explained problem videos I've ever watched
Thanks tony👍
These old school tips & tricks are good. Keep them coming.
Great stuff!. There's also the hopefully tiny gap between the rotor tip and the post in the distributor cap.
I believe this may follow under the sa.e heading.
I had a Caddy that ran fine but under a load it developed a skip.
Turned out that whoever installed the spark plugs, used a spark plug socket minus the internal rubber insulator. Cracked the external porcelain on half the plugs
Omg tony I never thought of that problem with a super coil, I replaced my super coil with a flamethrower which looks like a regular coil but has a shorter wire base, so maybe my super coils are good
Your timing is impeccable. (see what I did there?) I have this problem at the moment. Thank you.
Tony never ceases to be entertaining. Thanks Tony.
spray everything with squirt bottle on heavy mist in the dark. the firework show is often great, rev it up also.
Hey Tony, I really appreciate what you do, how you approach it, and how you teach it to others. Thank you.
incredible how much I've learned from utg's videos 😊
EXCELLENT VIDEO!!!
One cool thing I saw was a 'Vette on a rainy Calif nite, throwing a spark from the coil wiire to the intake manifold! Like 8-10"!
Hey UT! I have a question and im hoping you can help. I have a 67 Chevelle with a 750 holley double pumper with mech secondaries. My problem is that the car starts and runs fine, but when it warms up it starts acting like its a misfire, kinda even flooding? And it just wont idle or drive right. Ive tried leaning it out, richening it, but it seems like nothing helps.
SO true///you have been around man. for sure
I hope to visit UTG when I visit TN this fall.
That would be cool. I would if my travels ever take me to Tennessee.
Thank you for this video coming from a Mopar guy. My 96 2nd gen 1500 ram has been through some changes in the past two years of me working on it, tranny rebuilt, top end, head gaskets and so on... I got this truck from a friend who brought the 4 gen ram 1500. She had just got some work done to this truck, about 1500 dollars worth. New water pump, spark plugs and wires and radiator. When I saw this, I said to myself where was this mechanic going because shortly after I got the truck, major issues my friend. Even though I pitched the Crankshaft sensor wire between the tranny and engine, opps my fault... crank no start right off the bat. I'm like damn. So I checked my fuel, good there, checked my air, no clogs, checked for spark, no spark. Okay I got this , time to put on my big boy pants. Put in a new crankshaft sensor, oh I'm loving it, yeahhhhhh, I got a spark, thank you Zues...... lol. Then I'm thinking, something caused this but what,🤔🤔🤔🤔.... Then your video popped up. My number 3 wire, done # 7 wire burnt but still works... Then it hit me, you said if the spark has to jump then anything around it will become burnt. Just like in my case, the guy that did her tone up did not put the spark plug wires on good enough. I must admit on the 2nd gens 1500, just around the spark plugs there are those melt boots. Or a tube of some type, they are useless... They are the cause of those wires going bad, due to the top of the spark plug wire ends just before the top of the tube. But just think if your finger slipped off the wire as you are pressing the wire down and cutting your finger on the top of that boot. How many curse words can you say in 15 seconds after that happens. LOl thank you again brother for this Knowledgeable information.
Hey Uncle Tony, You can paint the top of that coil with about 3 coats of fingernail polish [ Your favorite color of course ]
Let it dry for 3 hours and it might make it usable again.
Hey make a Video of it if You like the idea.
Great stuff You're sharing with these younger greaseballs Uncle T.
Could you do a video on the Chrysler 400 engine. There isn’t a lot of information out there compared to other engines.
Chrysler 400 = Chrysler 383...just a larger bore/piston size. 400's have less compression than a 383.
@@lukepokrajac1057 I also want to know how build able it is.
@@Armwrestling_jd Very buildable Justin. Sky is the limit for a 400. Big issue is the low compression piston. Your piston are probably about .150 below the deck of the engine. This means low compression and less power making ability. I'm pretty sure they are higher compression pistons on the market now for a 400. 440 source heads will fit on your 400. They will raise compression even if you dont change pistons. It'll probably go from 8:1 to 8.5 compression ratio. Lots of articles out there on modifying the 400. They make excellent stroker motors. Largest bore of any big block Chrysler.
Gap between rotor button and dist. tower?
Back in the 1980`s they use to sell a set of wires that jumped a spark right before the plug in the JC Whitney . I guess it didn`t work too well because it never took off.
Got a neighbor who has a mustang with 2 /4's sticking out of the hood, comes by my shop ,sounds fine till he puts his foot in it,pops ,cracks ,misfiring. He asked for my 2 cents.told him it was electrical. Of course he rebuilt his carbs. unnecessarily. Said all electronics were new ,had to laugh. Cap was cracked, had him going in 10 minutes.
Same.......Damm caps😂
Extremely well done and informative video, thanks Tony
Would you get zapped when holding the plug wire looking for spark?
Yes if the engine is running
Absolutely .
Wear old pants and underwear , or , thick rubber gloves .
Fast method of checking tho 🤣
Yes and it will hurt like hell.
It's best if you stand in a puddle of water so you are properly grounded when you do this experiment.
Thanks for the solid info brother. You gave some wise knowledge on spark gonna help me out
Just cured a high speed power problem. Ran fine till I got up to cruising speed, didn't seem like a miss just no power. Had a non vented gas cap on an old vented system. Big whoosh when I removed gas cap.
Good stuff, but what about ballast resistors, though? They can go bad and cause similar problems. If you have a Ford, that 'make it really easy to steal me' block needs to be earthed where it attaches to the body, and this contains the ballast resistor. If it isn't, it will typically run for a minute or two, then cut out like you've turned the ignition off. You could also buy a car that's running a 1.5 ohm coil that actually needs a 3 ohm, or an added ballast resistor. The points will burnt out quickly and close up, causing sooty plugs due to a weak spark.
Back in the day I owned a charger very much like his but I had a street hemi in it,, doing a bit of street racing with it found that with about 10,000 miles on the plugs (champion) I would get misfires above 4200 rpm, and finally found that putting in a fresh set of plugs and could do ok for another 10000. When testing on a plug tester, could see that higher chamber pressures it would blow out the spark, this was using a std. coil and distributor.
I had a turbo car back in the 80's that needed new plugs every 1,000 km's or they misfired.
I just had a cylinder that was misfiring. This goes back to the EFI talk. My first action I grabed my IR gun and looked at my headers. Didn't see any big differences. So I did a compression test. Once again no big difference. ..? Called the EFI tech line. He said spray a mist of water on the header tubes. Thinking I already checked them, but did it anyway. #4 was much colder! Next grabbed a spark plug checked the spark. Looked good. Swapped two Injectors around. Problem didn't move? So then I pulled the plug and this time tested it. Had no spark then some spark. Plug was clean and looked good? Pulled the cap. #4 wire had a little crack in it and is next to the firewall & wiper motor. Jumping the spark. But not always? Put a new spare wire on, problem solved? Why was it missing? Driver's side motor mount was broke. When the motro reved up it moved closer. . Now you my wonder why #4 is back there. Well the xyz distributer has screws to hold it down. When it was made one screw was underneath the A- body wiper motor. So I set it up for #1 wire to line up with # 2 cylinder not #1. So all the wires are now two spots off. Pointing at #2 with #1 at TDC. Screw problem fixed, unless somebody else works on it.
Thanks Tony. Another lesson learned from your videos.
I suppose to limit issues on where you can't see the spark go from the wire to the cap, maybe the tower style plug attaching type of dizzy cap is worth the investment?
Dirty or rotted wires or a dirty, oily rotor cap can cause flashover though.
This is something easily seen by running the engine in total darkness.
The wires will sparkle all over if this is happening.
Short term, sometimes, you just spray some engine degreaser all over the ignition parts and wash all the gak off of them.
But if the wires are cracked and rotted, you need to replace them entirely.
That's a great video! I have to look at my Duster for a misfire under load next weekend.