# 4.2L Rough Idle and Misfires on Cylinders 2,5,6,7, and 8. Please Help



## fatcamo (Jun 26, 2012)

Hello everyone, I'm new to this forum and all forums in general so I'd like to say thanks in advance for any helpful advice! I'll start by giving a brief history of the car as I know it. I'm working on a 2000 A6 4.2L Quattro I bought it from a friend of mine in December 2010, it worked great for a few months. Recently I've been having issues with it and the CEL was on for a few months but I never had the ability to pull it because I'm in rural ND right now. I finally borrowed a VAG-COMM cable from a friend of mine in Alaska and scanned the codes. What I got from my mechanic was that the variable intake runner flaps were not working due to a vacuum issue. I replaced the vacuum lines on the car and when I did it sounded like it was about to fall apart, the idle was rough and down around 2-300 RPM. It was really scary to leave the car running but after a minute of two it started to settle down and started to idle normally. I still had poor throttle response and when it did pick up in RPM it wouldn't drop down right away. The second thing I noticed was the one of the intake runners was stuck completely. I took the intake apart and serviced the runner to make sure that i was moving again and after that the car still saw no change in performance and continued to throw a CEL. I pulled the codes recently and this is what I came up with. 

P1141: Load Calculation Cross Check Range/Performance 
P0300: Random Misfire Detected 
P0302: Cylinder 2 Misfire 
P0305: Cylinder 5 Misfire 
P0306: Cylinder 6 Misfire 
P0307: Cylinder 7 Misfire 
P0308: Cylinder 8 Misfire 
P1128: Long Term Fuel Trim Mult. Bank 1 System Too Lean 
P1130: Long Term Fuel Trim Mult. Bank 2 System Too Lean. 

Some additional notes. When I start the car it runs rough for a bit and then starts to smooth out, but if I start the car and then shut it off right away it idles right where its supposed to without any issues. The other thing that I've noticed about the car is that since I've had it the exhaust has always smelled really rich. I know there are a lot of issues going on here but I'd like to see if I can't solve the problem on my own without having to take it to a dealer because the closest one is nearly 10 hours away. Thanks again for all your help in advance. 

Matt


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## The Curse (Oct 24, 2005)

My bet is on a Crank Case Vent Valve right on the top of the intake manifold under the center engine cover. Most likely the inside rubber failed. The reason why it smooths out after awhile is because is going into a safe/limp mode. Only erase the codes after valve is replaced. Probably getting some nasty MPG too. Hope that helps :beer:


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## daboostedb6 (May 20, 2008)

vacuum leaks can lead to misfires. make absolutely sure you are dont have a vacuum leak or messed up one way check valves. i dont know if vag com can run basic settings,but if so check basic settings block 107, if ok then you have no vacuum leaks.this means that its most likely mass airflow sensor. to checkthis with scan tool,run basic settings block 32 which checks fuel trim. if the top or bottom number exceed plus or minus 10 and vacuum checks out ok, you will need to replace MAF sensor


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## daboostedb6 (May 20, 2008)

you could also try disconnecting the MAF and see how it runs after that. This WILL light up the dash and throw more fault codes but if the car consistently run smoothly after this, then the MAF may bre your problem. It is known for causing these problems especially when you have both fuel trim for both banks faulty


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