At a loss with this MAF & misfire issue - experts plz help

[zz2h33]

I've been battling a "MAF" problem with this car for some time now, and i'm finally ready to ask for some help because I have no idea wtf is going on with this thing. I say "MAF" because I really dont think its the MAF sensor. Here are the symptoms:

- In idle, multiple misfires and runs like junk, sounds like its got a huge cam, blip the throttle and smooths out and runs fine until it drops back to idle again
- Throws 7 codes: 300-304, 306, & 102 (misfires for all but cyl 5, and MAF low circuit)
- It will run like ^that^ until it disregards the MAF sensor (at least thats what i understand), i then get a solid ESP light and it runs great until i clear codes and it goes back through the cycle

What i've done:
- If I unplug the MAF, I get a solid ESP and CEL, and the car runs fine (aside from hard reverse to drive transitions on the TIP).
- Since it runs fine with the MAF unplugged, I've tried replacing the MAF with a brand new one but get the same issue.
- I thought I may have had a bad MAF out of the box, so i bought another one with the SAME result
- Replaced all my vacuum lines thinking it could be a vacuum leak, same result (plus doesnt make sense as it runs fine with MAF unplugged)

Before anyone suggests it, I had the CP recall done.

Any suggestions guys? It acts like the MAF is bad but I've tried two brand new MAFs.

[old guy]

Well it's definitely MAF related since you can unplug it and the problem goes away. Maybe the problem is with the harness going to the MAF. Might be worth investing in a Bentley so you can check out the signal to/from the MAF.

[EBG 18T]

Find someone with factory harness tester. This allows you to plug in between the ecu and the car and test each circuit/ harness individually.

[Lastsummer]

I've been battling a "MAF" problem with this car for some time now, and i'm finally ready to ask for some help because I have no idea wtf is going on with this thing. I say "MAF" because I really dont think its the MAF sensor. Here are the symptoms:

- In idle, multiple misfires and runs like junk, sounds like its got a huge cam, blip the throttle and smooths out and runs fine until it drops back to idle again
- Throws 7 codes: 300-304, 306, & 102 (misfires for all but cyl 5, and MAF low circuit)
- It will run like ^that^ until it disregards the MAF sensor (at least thats what i understand), i then get a solid ESP light and it runs great until i clear codes and it goes back through the cycle

What i've done:
- If I unplug the MAF, I get a solid ESP and CEL, and the car runs fine (aside from hard reverse to drive transitions on the TIP).
- Since it runs fine with the MAF unplugged, I've tried replacing the MAF with a brand new one but get the same issue.
- I thought I may have had a bad MAF out of the box, so i bought another one with the SAME result
- Replaced all my vacuum lines thinking it could be a vacuum leak, same result (plus doesnt make sense as it runs fine with MAF unplugged)

Before anyone suggests it, I had the CP recall done.

Any suggestions guys? It acts like the MAF is bad but I've tried two brand new MAFs.

I literally just started having the same exact problems tonight, no more than 2 hours ago. I have the 3.0 quattro and Ive heard that installing big filters or K&N filters can gunk up the MAF and cause them to go bad.
What did you end up doing to fix the problem or did you come up with a conclusion as to what may have been causing this?

[zz2h33]

Sorry I did not see that you replied to this thread. I'm still having the problems, I deal with it by driving it with the MAF unplugged. I do not have a Bently manual to troubleshoot the wiring harness for the MAF, but this is the last thing left to do. It cannot be the filter gunking up the MAF, I buy a brand new MAF, plug it in and it acts up immediately.

[Rausch]

What brand MAF are you getting? Do you have access to a scan tool to see what MAF is at idle and what your fuel trims are? make sure all your connections are tight on your MAF sensor and going to your throttle body. Also you installed the MAF sensor in the right direction.

[zz2h33]

What brand MAF are you getting? Do you have access to a scan tool to see what MAF is at idle and what your fuel trims are? make sure all your connections are tight on your MAF sensor and going to your throttle body. Also you installed the MAF sensor in the right direction.

Hitachi, no i do not, all connections are tight and MAF is in correctly (arrow points towards TB).

[zz2h33]

I'm resurrecting this thread because i FINALLY fixed this long time problem i had and I want this documented for others who may stumble upon this thread. It ended up not being a MAF problem at all, it was my PCV system...the typical cracked/broken PCV lines that plague these engines. I found a line cracked last week, ordered the replacement kit from ECS, installed yesterday and it runs like a champ now. I'm kicking myself because the car acted like it was a MAF problem ...would run like crap with the MAF plugged in, once the MAF was unplugged it would run ok. I've been chasing this problem for about two years, I've bought two brand new MAFs thinking I had one bad out of the box (which are now in the FS section). I rang out the MAF harness. Spent countless hours troubleshooting and scratching my head. All the while it was the damn crappy PCV system. Anyway it feels good to drive the car with no CEL finally!

BIG thanks to DIAGNOSTICATOR for the help!

[Kelz]

vacuum leak

check for bad vac hoses, bad brake booster etc.
also the PVC valve

It says low because the MAF sensor reading is not what is expected, using the speed density displacement x rpm formula. the ECM has a check chart of expected values.

[Kelz]

dude i am so sorry i didnt read that you figured it out. sorry.

[old guy]

dude i am so sorry i didnt read that you figured it out. sorry.

Well your diagnosis was good! I missed the boat on my earlier post. The cracked vacuum hoses were letting in air that wasn't being metered by the MAF sensor and consequently the A/F mix was wonky.