mikeyb

Hey guys I just bought a b5 s4 a few days ago and am having issues with boost at WOT. It is stuttering at WOT. Heres the back story. I bought it the drove it for few hundred miles then to my hometown 200+ miles away. It ran great the whole time no issues. When I got home I brought it to a self wash with a pressure wash style sprayer. I did not spray the engine bay. When I pulled out of the bay it started running funny like a misfire (shaking bad, loss of power, smelled like crap, sounded like a Subaru). I figured it was a coil or something got wet that wasn't supposed to. I parked it for a few hours and went out and started it, it ran good again so I drove it to town. When I got to town I parked it, and when I went to restart it about an hour later it ran like crap again. Turned it off waited 10 min. Started it and ran fine again. Went home then the next morning I went out and it ran like crap. I figured it would be a coil issue so I checked the coils by unplugging one at a time seeing what ones changed the idle. I found out that looking at the motor the cylinders on the left side were having problems the top cylinder didn't change idle bottom changed it a little. I replaced the top cylinder coil and it ran a little better. but still shaking and sounded like a Subaru. So I went to the next thing maybe fouled plug? I replaced the plugs with iridium plugs. no change. after that I guessed ICM. I couldn't get the ICM anywhere from parts stores so I went to a salvage yard and got them off of a A6 with the 2.7tt. (same part numbers) After I changed them the car ran great again but then started to boost funny. Like I said it stutters. It dosnt feel like its getting full boost either on some of the pulls. It only happens when you come into boost hard under heavy acceleration. Idk what to try next any info would be great thanks guys!

SnyperBob

Sounds to me like either a coil or a boost leak.

I had a torn TBB that caused me all sorts of problems. One day it would run fine, next it would fall on it's face under boost.

Here's the boost leak tester I used to find my leak

mikeyb

fixed the issue!