It is...

17536 p1128 035 bank 1 mixture adaption (multi): system too lean

I've replaced the air filter and the MAF seems clean, reset the code...then in about 2 days it returns. Any suggestions? I can replace the MAF and O2 sensor, but hate to pay for all that if it's not needed. The car is an 01 A4 1.8T and it runs great. Thanks in advance...

 

oh, and i just did the timing belt kit, fluids, and plugs are next...but the code was on prior to all of this...

 

That can often be caused by a leaking vaccum line, u should pop the hood and listen for a hiss. When I had that problem i could hear it even when the engine is running. Otherwise u can search google for "boost leak detector" or something and there is instructions on how to presurize the system to listen for leaks. This would be the first thing to try since it is the cheapest out of all of the solutions and its fairly likely that thats the problem.

 

+1^

https://www.audiforums.com/m_562674/tm.htm

 

i had the same problem, i changed fule filter, maf, spark plugs, cables. so far the proble is fixed no more engine codes, but if it returns the next thing to check is an axhust leak. how is your exhaust?