Hi all,
DESPERATELY need help here.
Have a 2002 A4 Avant 3.0L bought it with a blown timing belt...long story short, rebuilt motor, two new (used) heads (both bank cams and journals wiped out) all new parts, etc, etc.
NOW, it runs like a champ, nice and smooth, everything is great....been having a burning smoke smell while driving it....found oil leak evident at bottom of engine...traced up to oil coming from under the timing gear covers....pulled covers off and see a lot of oil in around the cam gears.....even though I put new cam seals and all that in when rebuilding motor.
Another VERY odd thing......with the engine running if I open the oil fill cap, the engine starts to misfire and stumble very badly. My 2.7T Allroad doesn't do that if I pull the oil fill cover.....
So, is that normal for the 3.0 to do that if I open the oil fill cover????
Could there be abnormal pressure build up in the heads which would push oil out of the cam seals even though they are new??? I did re-plumb the PCV system because as usual the plastic hoses were all cracked and broken so I made new tubing with rubber hose and all.
Sorry for being so long but I am completely stumped!!! I have been working on Audi/VWs for years and never have I had this much trouble with an engine.....I would LOVE any and all information/advice I could get.
Thanks in advance everyone!!
Rob

 

If your engine is running smooth for you with the oil cap on, and you know you have good compression, leak down, etc, no vacuum leaks in the intake system OR the pcv system, then you are good. It's not unusual for an OBDII engine to run rough (within reason) when the oil cap is removed. The computer sees that as a vacuum leak even though it's pcv system related. I have taken caps off other cars and noticed the same thing. I see you tried it on your other car, maybe try it on another car. It won't do that on an older car such as a non OBDII car is my bet, so it's got to be a 96-97 and up car in order for you to check this and notice the difference. That yours seems to run very badly is strange. I wonder if your oxygen sensor or sensors are not reading correctly?

 

Thanks Jeff,
I do have a couple of 2002-2003 Allroads with 2.7T in them...I tried it with them and they don't skip a beat. That's what made me think there was something wrong with this 3.0
Thanks for the insight.
Rob

 

The 2.7t's are designed to operate with high & low manifold pressures , the naturally aspirated engine only work on low pressure.