Fixed one issue, now I have another. A few weeks ago I was having a bogging/stalling/sputtering issue. Turned out to be the maf. Replaced it, and those problems and codes are gone. Now, Im getting misfires on all cylinders around 3500-4krpm. If I'm trying to boost it will hesitate a little and have a hard time spooling in this rpm range and then once it gets past 4k rpms it will clear up and spool and accelerate like it's supposed to. I've replace the plugs with auto light coppers gapped to .28 because I assumed that the bad maf problem fouled the plugs out. No difference. I wouldn't think its a coil issue since it's all 4 cylinders.

Now another problem I'm having at the same time is im getting a lean code, intermittent. And it's not my O2 sensor as my wideband will go lean randomly when driving. At idle it will vary between 14.5 and 15.3. I have no intake leaks that I can tell or boost leaks. Not sure where to start. Any ideas? I work for a used auto parts place so I'm going to grab 4 coils from work and see if it makes a difference but I'm not sure what the issue is. I feel like I could smell gas faintly while driving earlier but I couldn't see any leaks or anything and there isn't any more fuel consumption than normal.

I do have some exhaust leaks at the downpipe flange, but they haven't caused any issues before other than being annoyingly noisy

 

so just the lean code + the misfire codes? i.e. no more CEL's?

 

That and an downstream 02 sensor code but that's because I have no downstream sensor anymore Because of my exhaust setup. I have a feeling the two problems are unrelated though. I'm on my way to pick up a different icm to rule that out

 

Let us know what happens after that. I've had my share of misfire issues but Ive got a 2.8 so turbos can throw a whole different set of issues I don't know about.

 

Will do, it misfires even in that rpm range when not under a load so I'm not convinced it's a turbo ussue

 

Replaced icm, no change. However it was used from a salvage yard, there's no guarantee this one is any good either. Re gapped my plugs, and swapped the coils on cylinders 2 and 3 with some spares that I had(those 2 cylinders showed the most misfires under block 15 in vagcom) I did notice that when I started my car, my wideband showed 17:1 afr which is stupid lean, but after I held my car at 3000 rpm for 15 seconds or so when I was checking for misfires, once I let it back down to idle it stopped being lean. So idk. Sprayed all of the vaccum hoses with carb cleaner, couldn't find any leaks. Could a bad O2 sensor adjust afr enough to make it lean out? My O2 sensor is a cheap ebay sensor, but I know it's actually lean because of my wideband.

 

o2's can definitely muck up your system and cause odd misfire issues but evidently they take affect after a few minutes - so if the issue starts then it's an issue. At least that's what I understand... That being said, an new o2 sensor (I get bosch from amazon) certainly won't hurt, just can't be sure it'll fix anything.
Doesn't sound like spark plugs/wires/coils if they all started at once. Not the icm...
I'm guessing there was no oil on the plugs or general fouling of them...

Odd that running it for a bit stopped the lean. Can you try just letting it idle for the same length of time you revved it to see if it was indeed the revving or if it just needed to sit for a while - i.e. if it's a fuel pressure related issue - filter gummed up or pump not pushing out enough volume.

Some other sensor? Cam position? Coolant? Crankshaft position? It doesn't sound like any of those with the lean code. I'm leaning toward vacuum leak or o2 sensor.

 

Okay, so I replaced the O2 sensor with a bosche oem sensor and it solved the lean issue. However it is still missfiring on all cylinders between 2000-3500 RPMS... I have no idea why. Went ahead and replaced the icm, plugs(again) and all 4 coils. Still does the exact same thing. Coolant temp sensor is new. Would the cam or crankshaft sensors cause a misfire like this? I'm not getting codes for one but I suppose that doesnt mean much. Possible bad ecm maybe? It's extremely frustrating lol.

 

Great!

Damn.

Crankshaft position sensor can cause misfires but I THINK they're regular/common/constant. Don't quote me on that (i.e. get a second opinion).

You're telling me... https://www.audiforums.com/forum/b5-...speeds-216181/

If you find out what caused it, for the love of god let me know. I've been chasing this issue for more time than I want to think about.

 

Once I figure it out ill let you know lol. It makes boost lag so much worse through that area of the power band... Gonna try to throw a new ecm in it soon and see what happens