booost

Long time lurker, first time poster here on AW. Anyways guys, I was driving my car kind of hard the other day, and I lost power, EPC light came on and the car wouldn't run properly. It was sputtering until it died. I managed to get it into a commuter lot to scan codes and check the engine bay to see what was going on. I used a generic OBD scanner and got these codes/looked them up on rosstech:

16839 - EVAP Emission Contr.Sys.(Gross Leak) Leak Detected (I've had this one since I got the car, but next 2 are new)
17743 - Engine Torque Monitoring 2 Control Limint Exceeded
17965 - Charge Pressure Contr. Positive Deviation

I have done research on the issue, and so far I have checked all of my vac lines/hoses/TIP etc. and found nothing so far. I took out my old K&N filter which was dirty and replaced it with a paper filter. I also cleaned my MAF sensor with some cleaner, and reinstalled it. Now, the car runs better than it was, the EPC light is off now, but when I rev it up a bit, the RPM's drop and it just dies. When I unplug the MAF sensor, the car runs much better, not quite 100% but I can rev it up and it will come down to around ~800 RPM's and idle pretty smooth. I have read that this issue is mostly related to a boost leak/bad hose or pipe.

What do you guys think is causing this? Is the MAF shot? Potentially N75 valve or my DV? I'm going to do a boost leak test today when I get out of work, as well as reset the throttle body, but any info would be greatly appreciated. Thanks AW.

Nate (ETKA+Scumbag)

Check your N75 wastegate valve for the 17965 and your intake air temp sensor for the 17743 codes.

booost

Follow up:

Found out the DV became disconnected and I put it back together. The car is working fine now, it holds boost and runs great. I was doing some testing, and I was going about 40 in 4th, then popped it into neutral. The RPM's drop down to ~ 300, then they drop to 0 and the car completely dies while still rolling. Where do I go from here?

I heard from a mechanic that 2000 A4's with GIAC are prone to an ECU problem that causes this. I read on a few forums about it too so can anybody give me any insight? Thanks a lot.

AudiOsteopath

I had a similar issue on my 2.8L. Sometimes the idle would skyrocket and if i gased it during that time, it would choke out.

Looked everywhere thinking it was a vac issue, the ICV, or MAF. Replaced all vac lines, the ICF, and the MAF, and still the problem persisted.

Turns out the problem was the EVAP purge regulator valve (N75) was sticking open allowing exhaust fumes to recirculate when the engine would hit idle, making it lose vacuum and cause the rpms to go up to compensate.

There is a procedure on 12v.org to test the N75 with a voltmeter, which should also apply to the 1.8T. Easy to check and replace and worth a look.

Nate (ETKA+Scumbag)

Except, the N75 is what controls the boost on our turbo engines. You have a NA 2.8L engine.

There's a big difference here.

booost

I am definately going to check out the N75 when I get a chance. I forgot to mention before also that whenever I start the car now, in the morning or if I haven't driven it in a while it will sputter and the RPM's fluctuate from ~800-2000 (not touching gas). I'll shut the car off then restart it and the 2nd or 3rd time it will idle properly, and run completely fine (except for the aformentioned issue). Any ideas?

AudiOsteopath

Sorry, just used to referring to the EVAP purge regulator valve as N75. Is it the same for the 1.8T?