Searching for the S4's Missing Power | Redemption Series Part 1
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- Опубликовано: 15 июл 2024
- After posting up 219 HP and 240 ftlbs of torque on the dyno last October, I bring the 25quattro #audis4 out of winter storage to begin testing for possible issues that would lead to power loss. I validate the vacuum solenoid on the front of the intake manifold is working, perform a compression test, a leak down test and scope the cylinders for wear.
Featured shop tools:
Mityvac Compression Tester Kit - geni.us/mityvac-compression
Compression Tester Extension - geni.us/otc-comp-extension
Lang Tools Leakage Tester - geni.us/lang-leakdown-tester
Chapters:
00:00 - 2022 recap & test prep
06:01 - Flap solenoid test
08:43 - Compression test
11:10 - Leak down test
21:37 - Boroscoping the cylinders 
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I have a 2005 S4 Cab. with 46,000 miles and find that for no apparent reason one day it's on fire and the next day it feels sluggish. I had my pre-cats hollowed out with a JHM 93 tune 10 years ago and that made the world of difference. As to the timing chain rattle, I have never heard it once and I have owned the car for 15 years, bought it with 7000 miles. By the way, love how you approach everything, you seem very smart in your choices
Looking good, I was waiting for this video! I love your diagnostic process, and even though I've sold my Audi (2010 S5 4.2 6MT), I love these cars and your channel.
If your compression is in specs and the cylinder leakdown results are okay your next direction to go is to look at fuel trims. You may have a problem with fuel delivery, i.e. flow & pressure. I had a similar issue with my b7 2.0t. I ended doing a fuel system "refresh", new hpfp, lpfp, filter, and oem injectors. Made a worlds difference. Something to look into.
Thanks Ted, fuel definitely crossed my mind for testing after I get through the work I'm currently filming. I'll add fuel trim logging to the list.
Great explanation on where to listen for air leaks during the test
As a licensed mechanic that looks like cylinder scoring from the piston skirt side. If you pulled the pistons you would find that the skirts are probably worn. Unless you want to replace the block and or go oversize on the pistons just enjoy it
Yeah, the hunt will continue elsewhere but your recommendation is what I've already emotionally settled on: have fun for now without outright blowing it up.
@@FigureItAudi if anything you would have possibly some oil burning and or slight compression loss. Eventually if the skirt wears alot and I mean alot you maybe get skirt slap on the cylinder wall but I'm not even sure these engines are known for that. Sometimes the visual is scarier then reality. Where as if you didn't dyno and inspect the cylinders you would other wise enjoy the engine for what it is. NA V8 engine with a nice sounds and great history. I enjoy the channel Inspired my channel. Yours I believe is really well done and thought out. Continue the good work. I love to follow people and there cars.
Brilliant! The tension is palpable. Will I be doing this on my own B7...hmmmmm.
Some bad scoring there unfortunately. You can actually see the burr from the cylinder or the bit of debris at the end of the deep scratches
I also noticed that...more than anything I'd like to see the rings on that piston but they'll have to hang in there for now.
Hey friend, I'm just swapping my engine for my s4 25th. And I'm refreshing seals, and for over 100k miles, it's not bad idea replace old valve steam seals on new. It's easy, but get a time, and for that you have to release your chain, sounds scary)) but, on my mind- important
Helo I love your videos. I have A6 4.2 BAT try to look on fuel corrections on idle because when you testing the flap and stop the angine flap has to stay in closed position (i have a vacum storage to store vacum over night so flap stay closed the plastic valve on front of engine is one way valve for vacum when valve is okay you may have mayor vacum leak in vacum system on front of engine) these engines dont like vacum leaks .and test the MAF if its okay a had big power loss on new but bad MAF (stay with bosch)
Maybe check for intake air pressure leaks and exhaust blockage.
I have a 1998 A4 1.8t, I rebuilt the engine only 10.000km ago (6000 miles) and it had 238.000km on it (About 150.000 miles sorry I am European lol), but the cilinder walls did not look like that. They were pretty much scratchless even though it had quite a few miles on it. Didn't even have to hohn it, cilinders were fine. So I am kinda worried about your cilinder walls tho.... But I think these scratches can be hohned out which would be great
I have been waiting for this video.
Numbers don't look too bad on the lower side for two of them. Here are the Specs right from my Audi service manual (For this engine). New is 10..0-14.0 Bar, Wear limit is 9.0 Bar, Difference between cylinders is Max 3.0 Bar.
I am sure you covered it but a few things the service manual notes.
Engine oil temp at min 30 Deg C
Battery Voltage 12.5 (I saw you had the charger)
While testing "crank the engine long enough until pressure increase no longer appears on the tester"
I have the same replacement part for the upper rad hose. same small leak but seems to be ok if I don't disturb it. From what I can tell the O-ring that comes with it is not quite the right size and a replacement OEM O-ring should fix the issue.
Not that I can afford it right now but. JHM has an easter sale on for 15% off all in house products. The SC kit would fit nicely with the airbox already out of the way.
Yeah, the o-ring in the upper rad hose (I think mine is a Vaico unit) is maybe just
@@FigureItAudi The is exactly how mine acts too. My hose is REIN CHR0506 that I picked up off Rockauto. I haven't been bothered enough to change the O-Ring yet.
@@WarheadBMW Now that you mention it, mine's Rein as well. I may pass that feedback along to FCP (where I bought mine) and by some miracle, the. manufacturer can make a change.
Update on this: I replaced the o-ring with a CRP one of the same part number and also lubed the interior of the fitting somewhat liberally with synthetic grease and it seems to have done the trick.
@@FigureItAudi Perfect, That gives me hope for when I get around to replace mine.
I just finished with rebuilding my S4 B6 after cam chain guide failiure. My motor got about 160 000KM on it and it also got some markings in the bores similar to yours. The bores looked worse then it was. It wasnt any skratches more like the coating got discolored at some areas.
Thanks for the point of reference Fredrik.
Hello, I thought my S4 (2006) was dead since it showed 260hp at the dyno before ECU tuned, for 250.000km. and 292hp with the stage 1 ECU tuning.
Nevertheless, I can't wait to see the next video very interresting to see how you go through the process !
The next episode will be out this Saturday, July 15. I'd be really interested to see what your data results would be if you follow the same testing I did, since so much is dependent on engine and timing condition.
Still working on the CERATEC?
Did you end up doing some data logging on the road for timing values?
Yeah, that and a number of other ECU tests will be in the next video out.
175,000 Audi BEL 2.7T refresh recently and yeah man, you’ve got some bad scoring there. And maybe even a little piston slap or something going on in 2 and 4, maybe more.
If your compression tests check out, though, the leak downs looked good. Head scratch.
After I finish up the mods I'm working on right now, the next testing video will check out timing, fuel trim and some other longer shot causes. These first engine tests though at least confirm the old girl's a little tired.
The cylinder walls don't look very good, im no expert and even with the leak down and compression test I would say that's where at least some of the power loss is coming from
Also what's the track around 4:10?
It's a song called Galaxy Chaser by PALA. Not bad for stock music, right?
@@FigureItAudi It's great :D suits the good video's you put out !
Honestly, I think your cylinders look like pretty much every other B8 S4 V8. My bet is that the timing is off and it is likely because of timing chain guide failure.
Think you have a typo and mean B6/B7 S4. B8 is a supercharged V6.
The boroscope shows IMO bore scoring, which might explain the power loss.
Without removing the cylinder heads and visually inspecting there is no real way to tell if the scoring is terminal.
Your best bet is to find a reputable engine shop and let them tell you.
Agreed Aaron - No doubt some of the wear is worse in some cylinders than others - and granted some of the scoring *could* be deep enough to be felt by touch - but in the grande scheme of compression and power loss, I'm still skeptical it's a major issue right now. I had a suspicion the cylinders were in this condition during the last project and is in part why I opted to put a healthy amount of Ceratec additive into the oil. I don't mind keeping the engine 'roided out to keep it healthy for now.
@@FigureItAudi Not just that, If you happen to be burning oil at all (valve stem seals) I personally find that Liquid Moly Motor oil saver (2020) works wonders.