Helping out a friend of mine troubleshoot a rough idle/misfire on his AWM equipped Passat. Vag Com scan points to a significant intake air leak. I'm a V6 owner and am unfamiliar as to where some of the more common vacuum leaks are on the AWM. I can hear a hissing coming from under the intake manifold but could not locate a source.

Here is the full scan if you guys have any input:


VAG-COM Version: Release 409.1-S

Control Module Part Number: 4B0 906 018 DQ
Component and/or Version: 1.8L R4/5VT G 0060
Software Coding: 0016551
Work Shop Code: WSC 01023
10 Faults Found:
17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 001 - Upper Limit Exceeded
16555 - System too lean
P0171 - 004
17519 - Bank 1 sensor 1 too lean
P1111 - 002 - Please Register/Activate
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 001 - Upper Limit Exceeded - Intermittent
16684 - P0300 - 001
16685 - Random cylinder misfire detected
P0301 - 001
16687 - Cylinder 3 Misfire Detected
P0303 - 008 - Implausible Signal
16688 - Shareware Version. To Decode all DTCs
P0304 - 008 - Please Register/Activate - Intermittent
16686 - Shareware Version. To Decode all DTCs
P0302 - 008 - Please Register/Activate
16485 - Mass Air Flow Sensor (G70): Implausible Signal
P0101 - 004 - No Signal/Communication


I see the P0101 but kinda figured it was reading low due to lack of airflow by the MAF as most combustion air is coming from the leak.

Any help you guys can provide is greatly appreciated!

 

From what I'm seeing (lean all over): I'd try replacing the fuel filter first. It's cheap, really easy to do and it probably needs one anyway.

 

Grab a new MAF too while you are at it. Or even just give it a good clean. If you are getting a code for MAF, that could easily cause misfires and lean signals (I've had this happen to my own car). As for vacuum leak, I had one on my T bar (right above and behind the engine block. Kind of above the coolant temp sensor). And another L bar to the right of that (closer to drivers side).

*This pic was grabbed off the internet, so please forgive the crappiness of it. I know you said that you hear the hissing from under the air intake, so maybe this won't help you.

 

He found it! It was a broken hard plastic line under his intake manifold. It has been patched up temporarily until he orders the new hose. I still have to clear codes for him and I'll probably clean the MAF while I'm at it. Told him to pick up a new air filter as his was plugged pretty good. He's planning a tune up this spring but it is running much better now. Thanks for all your help guys!

 

I was just about to +1 the vacuum leak idea too! Good thing you found it (I've had the same problem before). Just buy some hose from your local parts store. It's cheaper and better than the stock line anyway.

Good luck w/everything.