2003 Audi A6 4.2L, 167k miles

A Couple months ago I was told I need a MAF by my mech, I pulled the codes and there was a P0101 and have since had a hell of a time getting things right. I'll skip over some of the interim stuff and go right to the latest where I have purchased a new Bosch unit from ECS Tuning. I had purchased a used MAF which didn't cure the problem so I thought it might have been a bad MAF. After the new MAF there was no improvement so I pulled codes and did some troubleshooting. Please help if you know where to go next. This is the troubleshooting circuit I did:

Old MAF(s) were throwing a P0101 code and some misfire codes

Install new MAF
Start Car, No lights, rough idle
As soon as I put the car in gear and let off the brake I get ABS + Trac Light
Turn eng off, Read Codes: P0300, and P030x on cyl 2, 4, 5, 6, 7
Reset codes
Start Eng, idle rough, no lights
Once I go into reverse I get ABS + Trac light
Drive 2 miles, 1 hwy, one city
Idle is now steady, Have TC + ABS lights
Read codes, have P0300 + P030x on cyl 5, 6, 8
Reset codes
Start car, idle is ok, no lights
In gear = TC + ABS
Drive 2 miles city
Idle is still steady
Eng off, pull codes, P0300 and P30x on 5, 6, 8
Clear codes
Idle is now rough - No lights
Driving = trac + ABS (ABS and Trac are not working when lights are on)
Drive 10 feet, no codes
Drive 3 miles
Idle a little rough, pull codes - no codes
Attached something on the side of the airbox I had missed, It was about 1.5"
diam and not attached solidly, comes in post filter.
ABS and TC now come on after 15-20 ft of driving
Drive 1 mile
no codes

Next Day I let the wife drive it as normal and she comes home reporting that the car is still acting like it did originally where the car does not want to accelerate and it holds gears too long

Pull codes = P0101 (No P030X codes).............. ARGGGGGGGGGGGGGGGGGGGGGGGGG!

I double checked and could not find anything I missed. Air filter is in decent shape. I could not find any bid post MAF air leaks (there could be a pinhole, I'm not sure how to test it) and I see no vac leaks... Any ideas?

 

Hi. Unless you have another faulty MAF Sensor or a bad/loose connection somewhere in the wiring harness , you may possibly have a faulty Intake Air Temperature (IAT) Sensor or G42.

It would br a good idea to double check your MILF codes to ensure this. The generic code for a faulty AIT would be (P0112 or P0113), meaning that the circuit has either a low or high input.

As far as the P0300, P0301, P03etc. codes, these are all indicative of a faulty coil pack on the related cyclinder or just a misfire caused by a bad or worn spark plug.

Maybe this input helps....Good Luck with it anyway.

P.S. In relation to the P0300 codes, was your car one of those affected by the recall related to faulty coilpacks?? Mine was (2003 2.7T) and the coils were all replaced free of charge by Audi of Jacksonville??

 

I've never had a P0112 or P0113 as far as I can remember, I'll check the codes again after another day of driving. I can't imagine I got two bad MAF's.. As for the P0300's it didn't come back with any after a day of driving so I'm not sure what to think. I'd prob clean the plugs and regap them after it running so shitty all this time.. Any ideas on how to troubleshoot further?

 

Incorrect MAF readings will cause a misfire so I suspect the MAF problem to be the root of your other issues.

Since you have already replaced the MAF and still have the same problems you have to think that you either have a wiring issue or a leak.

Or I could be wrong

 

I dug around a bit and gave up. I'm going to take it to my audi mech on Friday

 

So my tech used his VAG-COM to look at things... we found that the brake light switch was bad. I replaced that today and the ABS/TRAC light combo is basically gone now. The trac light comes on intermittently but the abs does not. He also did a throttle body adaption which appears to have made the maf work better with the car. However after putting ~100 miles on the car the P0101 is back on as well as P0174 and P0171's. I dug around for vac leaks or an intake leak post maf but I didn't see anything. I'm going to go back to the mech again soon. I runs much better now but it's still not in a sale able condition which is the whole point...

 

Dunno. I keep reading and keep looking at this and I keep coming up with the same conclusions, an electrical wiring problem or a leak.

post back when you find out

 

I'm trying a diff MAF now...I'll post what the resolution is when there is one..

 

Sounds like you need to find a tech that knows what he is doing.

To diagnose this issue over a PC is virtually impossible.

 

Yah, it's certainly not a cut and dried issue. If I stop making progress I'll just take it to my Audi guy and leave it there.