Need help...I am trying to help a friend out with an a4 he just bought......

[elijahallen]

but am having a hard time diagnosing a problem with the car. He just bought an 01 A4 Avant manual 1.8T. The car broke a timing belt and was sold to a guy that had a shop but mostly worked on trucks. He put a used head on the car, I don't know more then that as far as the condition of the head. The car had random misfires on every cylinder and a code for intake cam over retarded and a running lean code. When codes are clear the car bucks and jumps as you try to accelerate. As the check engine light comes on and goes off storing codes the car runs smoother and smoother but stays in limp mode. The N75 valve is bad but when I change it out with two other valves each time the boost is different, one valve makes it boost to 20psi, the other two make it boost at 5-9psi. Power is the same at 20psi as it is at 5psi. I pressure tested the system and there are no boost or vacuum leaks. I put the #1 piston at top dead center and the timing marks line up. Any idea's what could be going on? I am suspicious that the intake and exhaust cam are a tooth off from each other but have not pulled the valve cover off to check. Thanks for any help/suggestions.

[ricekikr]

a code for intake cam over retarded and a running lean code..

Your first clue. Check the timing marks (both timing and cam chain; leaning towards cam chain timing)

[elijahallen]

I checked cam chain timing and crank cam timing and both were on. Pulled injectors and intake manifold and went through all vacuum lines and connections. Everything seems fine and anything questionable I replaced. I'm now thinking it must be ecu, CPS, or cam chain tentioner. When codes are cleared the car will hardly drive, it bucks and stumbles. After codes come back the car adjusts enough to run smooth and boosts 7 psi. I am stumped.

[offroader1006]

If you have a Cam retarded code, and your timing is on, then the cam sensor should be suspect. no point fault tracing every direction of a symptom when you have a code in front of you.