See edited copy original post below:

Car is a 1998.5 a41.8tqm
Both 02 sensor and maf recently replaced.

On my xmas trip to NorCal I encountered this:

When I try to restart the car after filling the tank I must crank for 20 seconds while pressing the gas pedal. The motor coughs to life, but will stall if I don't keep giving it gas. Finally it smooths out after another 20-30 seconds.

I dropped the following code:
17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 35-00 - -
additive value is around 14-14.5%
I can clear the code, sit at idle and watch vag-com block 032 - the correction factor creeps from 0 to 14% in a minute or two.

My observations:
Problem occurs whenever I fill-up, whole tank, half-tank, quarter-tank, makes no dif.

idle varies in the 900-950rpm range. Seems like a vacuum leak, but I did a thorough check, warm and cold by spraying tons of carb cleaner everywhere I could think of - no dice!

If I stop, turn off the car, wait 3 minutes, then re-start, the problem does not occur.

If I stop, turn off the car, remove the gas cap, wait 3 minutes, replace the gas cap, then re-start, the problem does not occur.

But if I put gas in the tank, it will be hard to re-start.

I disconnected the battery for 30 minutes, cleared codes, and re-adpted the TB - still acts funny at idle.

Fuel filter replaced - no affect.

I'm now looking into a fuel tank vent or evap/purge valve that is stuck open or closed.
I plan on testing the fuel pump, fuel pressure, and looking at the filter screen in the tank as well... Just have to contrapt some adapters for the pressure test.

A previous suggestion was to check the wires at the MAF connector - they seem fine.

I also plan to remove the TB, and try to clean what I can. It seemed like and idle air bypass might be clogged or stuck - I'm not sure how idle air is regulated on this car tho.

Comments?

 

Either the wrong MAF was installed (did you compare part numbers to the old MAF?), or a hose is loose, and you're drawing in unmetered air.

 

I've had the new MAF for 5k miles or so, problem is much more recent. My understanding was that Bad Maf = Bad mixture across the board under load, not just idle. My block 032 (mult) corection value was 4.7% before I cleared codes last time.

I'll do a 3rd gear run and log the flow tho... might show me something.

Thanks!

-t-

 

You seem to be touching on the common issues. I would agree a leaking vacuum line might be at fault. Also examine the vac lines on the fuel pressure regulator (or just replace them). Low fuel pressure might be causing this...though I can't quite explain the circumstances you mentioned are causing the issue.

You asked about idle control. There is a separate valve that controls idle air flow. Do a search for Kris Hansen. Find one of his posts, and in the sig line, you'll see a link to his website. Go to his tech section, and there is a DIY cleaning procedure for the IAC valve. I *believe* the 98 2.8 has it, but I'm not 100% positive. If it doesn't have an IAC valve, then the idle air flow is controlled by the ECU and a little motor on the throttle body that adjusts the opening of the throttle plate. This motor is very delicate, so don't touch the throttle plate when you're cleaning it...if this is what your car is equipped with.

 

The vacuum leak seemed the most obvious suspect to me, but the fact that the hard start occurs after fueling is confusing.

Usually I can find vacuum leaks by spraying carb cleaner everywhere in the intake loop. But that didn't reveal anything, so I figured maybe the leak is IN the intake tract, maybe egr or idle air bypass.. etc...

-t-

 

IIRC, the 12V motors used the IAC valve. The 30V uses a little motor strapped to the throttle body. So you're back to the hidden leak now.... :-/

 

Did you ever resolve this issue? I have a 98.5 1.8tqm that just started doing the exact same thing.

 

I have the same EXACT problem. I also have a 1998 audi a4 1.8t. Whenever I put fuel in my car it wont start right away. I have to keep giving it gas for a few seconds for the rpm's to settle down. my cel light is on. same codes as yours. lean system. thought it could be the fuel pump but that wasnt the problem. I still have this problem. I dont know what it could be. My 2 guess is the MAF sensor or the EVAP PURGE VALVE. Im thinking more towards the evap purge valve. Im trying to look for this part. If you fixed your problem PLEASE get back to me ASAP. Thank you.

 

Same problem here.

I do know that I have a vac leak. The problem is I've troubleshooted and gave up.

The car runs fine. It's just after refueling that sucks.