I had my car in getting paint work for a week after a clown in a pickup truck scratch my door with his bumper. I got the car back and it is misfiring and hunting after the car haa been driven for a half hour or so. It is definately temp related. It gets progressively worse the warmer the car gets. So i unplugged the maf with the car warm and it idles smooth as can be. I plugged the maf back in and the rough idle hunting comes back. I replaced the maf and air filter and that make a very small difference. I reset the codes and trims with an obd reader and also un-hooked and reconnected the battery with no change. I checked the plugs in the engine area and the battery area and they appear good. The body shop did have the battery disconnected and ot appears good.

If it were an intake leak i would expect it to be there all the time regardless of temp. Another weird thing is the misfires seem worse with the AC off. Alternator? Battery? Coils? Any thoughts?

FYI: plugs, maf and dvs are new.

 

Did you reset the ABS codes? If you have larger injector or 5bar reg it can take some miles for the ecu to re adapt, A/C on bumps the idle air up so if rich this will lean it a bit. I hate body shops nothing but bad stories from myself and other trusted people. Sorry to hear hope you get it sorted.

 

Get an over rev reading rIght away to be sure the shop didn't joyride your car

 

I checked the mileage and it was in check.

 

Good point there! VAG do you have a durametric cable?

 

No recent overrevs. I did see that I am getting cylinder 1 and 2 misfires and a p0135(Oxygen sensor heater in front of catalytic converter, bank 1). It appears that the heater on the O2 is intermittently opening up when the car is warm. I can't figure out why I would only get misfires on cylinders 1 and 2 though. But hell, O2 sensors are cheap. I'll replace both primary O2s. It is one of those parts that will go bad eventually either way. And at 68k it is about time.

 

I'd still check for over-revs.

 

I checked them today. Less than 20 type 2s but they were over 1700 hours ago. No recent overrevs.

 

Heater codes can mean a cable/wire is open... check the connections to that O2 sensor.

And yeah 68k you might as well

 

I just "re-sensored" my car with new maf and o2's and it made a noticeable drivability improvement!

 

Tuned? > 15000 miles? Change plugs...

 

I am running an EPL tune. And the plugs, maf and air filter are new. I am getting an o2 sensor heater element code. I am changing sensors next week. A littlw FYI about these cars. The primary o2 sensors on bank 1 and bank2 are also the source for EGT calculation. So a failed o2 sensor can send erroneous EGT data to the ecu. If the ecu thinks the EGT is too high it will throw more fuel into that bank because it thinks the engine is running lean.

 

John, is it still running rough or do you just have the codes?

Scott

 

I changed both primary O2 sensors today. The car is running great now. No more wierd hunting at idle or misfires. I am still baffled by the fact that I was reading misfires on only cylinders 1 and 2 with the bad O2s, but stranger things have happened. I previously mentioned that the Bosch ones are the cheapest option and are a direct no wiring needed swap. I ended up ordering them from Advanced auto parts for $92 a piece(Bosch USA PN: 17044) and here is what I found to my surprise when I looked at the sensors.


Note the 996 part number directly on the sensor. They are exactly like what I pulled off the car. So add this to your notes when it comes O2 sensor time. I added the Bosch OEM part number information for the primaries and secondaries in the knowledge forum.

 

CELs and codes to diagnose O2 issues are limited.

If you scope the sensors and look at the analog signal and how it fluctuates over time it is a much better way to ID degradation that may be affecting running, but not yet throwing a code.

I've always use OEM Bosch for all german cars..plug and play.

A