50PSI compression on all cylinders...WHAT?

**A4INGS** · 09-28-2016 09:26 PM

Hey guys- hoping for some help here. I have a 2010 A4 that is APR STG2 and it recently took a dump on me. I decided to take my b8 a4 on a business trip rather than renting a car. oops.

Monday: Drove it 6 hours, about 80mph. Nothing out of the normal. Went ahead and changed the oil the week of my trip.

Drove like normal on tuesday and wednesday.

Thursday: Was driving the car to my business spot in Charlotte NC, and the car misfired. going about 75 on the highway, just cruising. The CEL started flashing, so I limped it off the highway. The car was misfiring pretty dang badly. Turned the car off. shook my head, hoped it was a dream, and tried re starting. Still misfiring. I let it sit for 5-10 minutes. Tried to restart and it wouldnt start. Smelled like 93 octane. So, I decided to get it towed. Took it to a local shop that knew european cars, but couldnt get it to the dealer without a wait.

So: Here is what we did.
1) Scanned the car. tons of misfires on cylinder 4. It deactivated cylinder 4. misfires on other cylinders as well. Coilpacks, right?
2) replace coilpacks with genuine Audi, latest revision.
3) replace sparkplugs with new NGK BK6REs.
4) test drive: car would still sputter and wouldnt want to idle. Not fixed.
5) ran dry compression check: WHATTTTTT! 60,50,60,50psi on cylinders 1,2,3,4, respectively. This engine has 88k miles on it. I have changed oil religiously on it. Never overboosted, only APR stage 2 tune on it. Havent done any audi recall-type stg1/2 oil consumption repairs on it. FYI, I only use 1 qt per 3500-4000 miles.

6) looked at the cylinders with borescope. they looked like they were caked in carbon.
7) I decided to drive the car for a bit and see if something loosened up. It drove fine on the highway, but wouldnt idle well. I did some thinking, and decided to drive it home after the business trip with a bad idle. Made it 6 hours home just fine. I just wanted to get the car home in my garage.

8) did some research. Double checked compression in my garage. Still low. Decided that low compression could be one of a few things:
a) head gasket (it's all 4 cylinders, so unlikely)
b) rings (wouldn't I see a gradual decline? also, I only have 88k!)
c) valves (could have a crazy amount of carbon buildup or all bent valves?)
d) jump in timing (possible with these engines)
e)bad compression tester

So, I decided to go ahead and pull the intake manifold. The valves were NASTY. About 1/8" of carbon buildup on the walls of the intake. I have now cleaned up the intake valves/intake and am ready to reinstall the manifold. I have learned that carbon cleaning is no joke.

I have been doing some timing research recently and got scared that my timing tensioner had gone bad. I checked each cylinder with a borecsope. No evidence of piston vs valve. Whew.

So, before I start putting things back together, can you advise of anything else to check for if I'm getting approx 50psi across all cylinders? Any help would be greatly appreciated.

**pierreb** · 09-29-2016 06:31 AM

Probably tensioner failure. Find a low mileage cyl head and swap it. I got mine for $650 shipped, with cams. Obviously do the tensioner, chain and guides too.

**S4'ed** · 09-29-2016 07:09 AM

Incorrect valve timing will give you low compression in all cylinders. Pull the bottom and top chain covers and check the timing marks. If the timing jumped only a small amount, it is possible to not have valve-to-piston collision........

**TheFugitive** · 09-29-2016 09:01 AM

Originally Posted by pierreb

Probably tensioner failure. Find a low mileage cyl head and swap it. I got mine for $650 shipped, with cams. Obviously do the tensioner, chain and guides too.

This take me down bad memory lane. I didn't follow this advice and dealer charged me 2k total.

**A4INGS** · 09-29-2016 09:18 AM

Thank you for the replies!!

Since I don't see any evidence on the pistons of piston-valve contact, would it be best to replace the tensioner only? Or just bite the bullet and replace the entire timing chain and accessories for $650?

Dumb question: why replace the head if there is no collision?

**pierreb** · 09-29-2016 09:21 AM

Check the timing first. Replace tensioner chain and guides. If that's still not fixing your issue, get your cyl head replaced.

Personally I'd just get the head replaced along with the timing hardware but that's because your head already has some miles on it and also because you might still get misfires. I guess it depends on how long you want to keep the car.

**A U D I** · 09-30-2016 07:07 AM

I would agree, check the timing first. You need to know if it's in time or not before proceeding. 50 psi across the board sound like you are using a flexible compression tester and not a hard tube one. Most of the time a flexible one will not tighten down well and leak compression when testing. I wouldn't keep driving it though. If the timings off and the head is not damaged it can jump again and take out the head.
Keep us updated.

**A4INGS** · 10-15-2016 05:21 AM

Update: finally had time to pull the front end this morning. The upper timing marks match up. Woo hoo. However, the upper timing chain definitely feels loose. Is it supposed to? I'll shoot a video in a little bit to better describe it.

**A U D I** · 10-15-2016 07:45 AM

That's the updated chain so it should be really tight seeming. I would check the tensioner to see if it has failed. I would be surprised if it's an older version because the chain is newer though. You can pull the plug on the lower cover to check it with out taking the cover off if you want.

**nycaudi** · 10-15-2016 04:11 PM

Bro, I'd change the cam shafts bridge while you're in there. Chances are, your screen broke and it's swimming in there somewhere.

06h103144j

I mean, you got that bitch wide open......start upgrading to latest revisions.

Future proof is never a bad wave to ride

**A4INGS** · 10-15-2016 07:26 PM

Originally Posted by A U D I

That's the updated chain so it should be really tight seeming. I would check the tensioner to see if it has failed. I would be surprised if it's an older version because the chain is newer though. You can pull the plug on the lower cover to check it with out taking the cover off if you want.

How does one check to see if the tensioner failed?

Also, I snapped the dipstick tube. 65 bucks for a new one!? Yeow! My older 1.8ts were like $5.

**A U D I** · 10-16-2016 01:02 PM

You can remove the plug on the left side of the lower cover to expose the tensioner. Push on it to see if it moves easy in and out.

**S4_SH1640** · 10-16-2016 01:43 PM

What is the range for a good compression on a cylinder? Where should you be at?

**A4INGS** · 10-16-2016 02:36 PM

Originally Posted by S4_SH1640

What is the range for a good compression on a cylinder? Where should you be at?

It should be 100psi+. New is 200psi.

**A U D I** · 10-16-2016 07:40 PM

Audi states below 90psi is bad, but I never see them that low. Most normal "healthy" motors are 160psi to 180psi.

**A4INGS** · 10-22-2016 11:23 AM

Update: replaced the timing chin tensioner this morning. The old one didn't seem to be malfunctioning or anything of the sort, which puzzles me. I uploaded a video of the old tensioner when hand cranked. Based on the pictures, does timing look OK?

**A4INGS** · 10-23-2016 09:24 PM

Anyone?

**A U D I** · 10-24-2016 12:43 PM

Your timing marks look good from the pictures. The lower picture was a little hard to see well. The video of the tensioner does not really show it move because you barely moved the crank in the video. That is the older tensioner that is prone to early failing though. Weird you have a newer chain on it. Did you have to set the timing when you did the tensioner or was it in time ?

**A4INGS** · 10-25-2016 05:34 PM

Originally Posted by A U D I

Your timing marks look good from the pictures. The lower picture was a little hard to see well. The video of the tensioner does not really show it move because you barely moved the crank in the video. That is the older tensioner that is prone to early failing though. Weird you have a newer chain on it. Did you have to set the timing when you did the tensioner or was it in time ?

Timing looks spot on. The arrows point to the center of all 3 black links. So, the chain hadn't skipped timing.

This brings about the question: if the timing hadn't jumped, could the car still run poorly with a bad tensioner? The old tensioner definitely wasn't keeping the chain taught when I hand cranked the engine.

**van462** · 10-25-2016 06:57 PM

I can't tell well from the video but where you rotating the pulley clockwise as you look at it. The chain tensioner only controls the chain slap on the slack side . It is a direct pull from the crank to the intake cam and across to the exhaust cam. The tensioner will help keep chain tension as the exhaust cam valve springs cause the cam to try and jump forward. With a loose tensioner you can usually see the chain on the exhaust cam come close to skipping teeth when rotating clockwise.

Also remove your spark plugs, it makes this about 50psi easier.

**A4INGS** · 10-27-2016 09:41 PM

Question: is the tensioner supposed to be this far out? Or would a new chain be recommended?

Also, for those who have already update the tensioner: how/where did you place the metal clip on the tensioner? It seems odd for the timing chain tension to rely on a clip that's under 1/16" thick.

**van462** · 10-27-2016 09:56 PM

The spring inside the tensioner is doing the real work. The clip is like a safety paw. In the event of high chain load it will prevent the chain tension from compressing the spring, under low chain load the spring applies pressure to the chain and as the chain stretches it continues to extend and the clip will move to the next groove.

**A4INGS** · 10-29-2016 09:57 PM

Fingers crossed... filling her with oil tomorrow after the sealant is done drying. Then, start up and test drive.

**A U D I** · 10-29-2016 10:27 PM

Hope it goes well for you !

**A4INGS** · 11-09-2016 10:12 AM

Originally Posted by A U D I

Hope it goes well for you !

The result: good and bad. The car runs. It still misfires and is running rich.

I'm going to do another compression check on it and a leakdown test. I'm confident that the timing is correct now and there is no gunk on the valves/intake.

I may drive over to APR (45 minutes away) and see if they recognize anything. I think $100 for a second opinion from them would be worth it.