vent hose issue
 

hi. yesterday i changed a vent hose on top of the engine on my 2001 a4, since then , my car starts shaking when i turn on the ignition and the check engine light keeps flashig for a minute or so then the car goes back to normal. i know i have a systen too lean code. has any one experience what i'm dealing with now . please help

Sounds like you're misfiring chief.

Pull codes?

I have code p0170. and multiple misfires on cylinder 1,2,3

code p0170 fuel trim bank 1

Hi there. I was dealing with a similar issue for months until I figured mine out. When starting it would misfire a bunch for a couple minutes, then calm down. But even while driving it would still act up for me. The only codes I had were the same as yours, system too lean, multiple random misfires, and misfires pistons 1-4. For ages I thought it was my throttle body, but it turned out to be a combination of a vacuum leak (which sounds like you may have fixed) and my MAF.

When I found my leak, and replaced the hose the misfires stopped, and so I cleared my codes to see if any would come back. Once I had cleared my codes, the misfiring came right back. Thats when I swapped out my MAF with one I found from a wrecker and since then I haven't gotten any codes and no misfiring.

I hope this helps! But as an added disclaimer, there is always the possibility that your issue is different than mine was.

@ soulstep . did you replace your spark plugs. also can you direct me to where the maf is located?

@ soulstep. can you explain to me how it would act up while you were driving, when i was driving mines it would start shaking between 45-60 mph . only way it would stop was if i kept the car at 61 mph plus.. sorry to keep bothering you. trying to fix my baby so we can get back to driving

Pikollo,
I replaced my spark plugs last year, but not when I started having my problems. You can check them if you'd like though. Pull them out and see if they are worn or have oil on them.
My car wouldn't act up consistently while driving. Sometimes it would be fine for a long time, and all of a sudden I would lose power for a bit, or it would become jerky. Kinda felt like a really crappy standard driver (i.e. car jerking lots when accelerating).
The MAF is located right above the air filter in your air intake box. It's on the passenger side of the hood. If you don't have the special torx screws that are required to pull out just the MAF sensor, you'll have to pull apart the whole box and check it. Mine had oil in it, which is why I think it was fried.
Here's a good DIY for it: DIY: Replacing MAF and/or air filter on 1.8T

Don't hesitate to ask more questions, I'm happy to help.

@ soulstep. thank you so much for the info

Let me know how things go!