2004 VW Passat (B5) need help fixing MIL light, rough idle, system too lean

benknight87benknight87 Member Posts: 1
edited October 2015 in Volkswagen
Hey there, I'm on a crusade to fix my own car this time around. Shortly after a long road trip in hot, dry weather, my car's MIL light came on. I brought it in to a local shop for a full diagnosis, and I have the following codes:

17705/P1297 Pressure drop between Turbo and Throttle Valve- upper limit reached.
17519/P1111 O2 sensor regulation Bank 1 System too lean- lower limit reached.
16684/P0300 Random/Multiple Cylinder Misfire Detected-Intermittent.
16685/P0301 Cylinder #1 misfire detected- Upper Limit Reached- Intermittent.
16686/P0302 Cylinder #2 misfire detected- Upper Limit Reached- Intermittent.
17544/P1136 Fuel Trim Bank 1 (add) System too lean- Upper Limit Reached.
16555/P0171 Fuel Trim Bank 1 System too Lean No Signal/No Communication.
16687/P0303 Cylinder #3 Misfire detected- Not a Plausible Signal- Intermittent.
16688/P0304 Cylinder #4 Misfire detected- Not a Plausible Signal- Intermittent.

The mechanic checked and there are no issues with the spark plugs. They did a smoke test and determined there were leaks in the PCV/breather system.

Here are the symptoms I've noticed:

1. Rough idle – this is the most noticeable one. My car definitely did not have this much engine stutter before the MIL light.
2. Strong smell of exhaust on startup. I can't say for sure this wasn't present before the MIL light, but it seems rather strong and could be related to the system running too lean.

Recommended repairs from the shop are:

1. Remove and replace kombi valve.
2. Replace breather system PCV components

So far, my uncle and I replaced the kombi valve and the crankcase vent valve. We also manually checked various breather pipes and hoses and didn't notice anything out of the ordinary. Unfortunately after these repairs the MIL light is still on and the symptoms described above are still present.

At this point I'm unsure how to proceed. Replacing the entire breather system is a lot of manual labor that I'd like to avoid. It's easier to focus on replacing single components and hoping for the best. I'm considering replacing the MAF next.

Can anyone give me any advice based on this description? Any clues what might be specifically wrong?
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