So I have a 2001.5 Audi A4 1.8t AWM non-quattro. It only misfires on the 2nd cylinder at idle only. CEL flashes while idling. Sometimes CEL flashes within 20-30seconds of idling. But sometimes takes up to a minute to flash. So this is what I have done to try to figure out why 2nd cylinder is misfiring at idle only. I have replace both O2 sensors, MAF sensor (my old one was dead), air filter, spark plugs, switched fuel injectors, coil packs, I have replaced many vacuum lines also and can't find anymore leaks. I even switched spark plugs for maybe a gap issue. When I pull the vag com codes It is only cylinder 2 misfire P0302. No matter what I change. So I did a compression test and it was a rented tester and it wouldn't hold the compression on the gauge but I could see it and it would go up to 100psi on every cylinder but 2. 2nd cylinder would only hit about 82-85psi. It was hard to see and no one else around to help me. Believe me the button to release the pressure was not being pushed.

This is where it gets interesting. I went on a hour and half trip with the A/C running. My check engine light turned off and never came back on while the A/C was running. When I turn the A/C off it starts misfiring. I have done a lot of reading and thought maybe its the ICM but my car doesn't have one. So I have no clue what to do next. Now I thought maybe sludge in the intake or valves or bottom end of the motor. Seafoamed my gas, my oil, and my intake. Intake I sucked it up through the manifold while the car was running. I noticed my turbo smoking at the exhaust side. Not the exhaust manifold but right where the turbo connects to my downpipe. I then drove it after I let it sit for 15minutes so I could run the seafoam out of the intake. Still misfires in 2nd cylinder only.

Now it makes me think is the misfire at idle only caused by a leaking turbo gasket?

By the way the car has 147k miles now. If it is a leaking turbo gasket should I just replace that or the turbo. I read at a couple of other forums my turbo is really hard to rebuild. Would have to drill something out. If you can't rebuild then I would rather go with a K04. What am I looking at the best place to get a K04 for a good price and do I have to make any changes to my ECU via Vag-com?

I should Add that my intake has oil in it aka car is pushing oil. Which I am sure is not suppose to be. Thought it was probably a bad turbo gasket which is why I am looking at rebuilding the turbo or getting a different one.

 

Your symptoms are completely confined to cyl 2. You have an unreliable compression check that picks on cyl 2. There's not a good reason to move on to the turbo, which affects all 4 cyls equally.

I think you should take it somewhere and pay for a reliable compression check. Play out the one bit of data that points to cyl 2 before you toss more expensive parts at this.

 

first things first. remove #2 coilpack, swap to #1 hole. see if misfire follows

 

Redline I tried that.

 

I'm having a very similar problem, only on Cyl. 4, but at around 2k-3k RPMs, and it's intermittent. Most of the time it does it, sometimes not. I've switched the fuel injectors, coils, plugs. I have a compression test kit on the way to me now. I have found oil below the throttle body where the hose connects and in the hose itself. My suspicion, outside of a compression test, is the oil is slinging up past bad piston rings and fouling the plug.

 

FilmmakerJWA Your issue sounds like a vacuum leak. But your compression could be shot also. If my issue is really the compression as in the piston ring is bad or a valve is stuck or leaking in someway then its time for a rebuild. Well. I decided last night to get new gaskets for my turbo and bought a K04 turbo for it since I have heard its really hard to rebuild the K03s.


So I don't understand why is it when I run the A/C my motor doesn't misfire? Doesn't that seem strange to you all? Also if it were a bad piston ring or valve wouldn't it misfire all the time not just at idle? My spark plugs do not have any oil on them either.

 

I've considered that maybe it's turbo-related, like a bad N75 valve or something similar, but don't understand why it would effect only one cylinder and not all. The compression test should provide a lot of answers.

That's weird it only happens when the AC is on. It sounds like the additional strain the AC is placing on the motor is causing something to go beyond a very low threshold. I doubt it's electrical, but who knows? Could something electrical with the AC cause an intermittent signal to that one cylinder?

 

what kind of condition is the spark portion of the harness in? these cars are getting to the age where the wires get cracked and can get very brittle

 

Now if you are talking about the cable that plugs into the coil plug. The clips are broken and that may be causing the issue since it is only at idle. Will keep you guys updated after this weekend. K04 upgrade. Then if I can figure this misfire out I am going to get a apr chip. Anyway to increase the stock 7 or 10psi boost without a chip?

 

Mine did the same thing. Worked after changing the coils and plugs for a little while and then just started misfiring again. My worst fear is I see these cars have had numerous problems with rings going bad. I'm wondering if oil is getting past the rings and fouling the plugs. I do have to add oil about every 1000k miles. I've heard this is normal but I've also heard it's not. So I'm at a loss on that one. I guess the only thing for me to do is take it to Audi for the consumption test. But if I figure something out I will keep it posted.