I had a low idle/stumbling problem a few weeks ago (no codes being thrown) i unplugged my MAF, drove it for a day and it seemed to run better so i took it out cleaned it, cleaned the TB and replaced the air filter.. ran MUCH better.. Then this week i found a good deal on a used Volant intake. after a day of driving with it installed i get a MAF code (low circuit voltage) and an evaporative emissions code (small leak) i checked the plug on the MAF thinking i may have left it loose and cleared the codes, all was well for a couple days but then the SES came back on, i read the codes again expecting to see the same 2 or atleast 1 of them.. but now it's P0171 (system lean bank 1).. is my MAF on it's way out? or is this in some way related to the new air intake? kinda strange that i've had no codes until the MAF cleaning and volant install... any ideas? Car is a 98 T/A A4, pretty much stock except for SLP LM1 and Volant intake...also the temperature here dropped drastically around the same time not sure if the weather could be related..

 

Check to see if u broke the little wires on the inside of the maf sensor they are pretty fragile

 

Thats kinda what i was thinking, i might have disturbed something. I'll check to make sure tomorrow but i dont think i broke it i just soaked it with a can of cnc maf cleaner.. if it was broken wouldnt it throw the low voltage maf code again or similar? also now im wondering if it was a maf problem would it be only causing 1 side to run lean or would i also be getting the p0174 for the other side?

 

Try unpluging the maf sensor and see if it idels better its more than likely your maf

 

Idle has been fine since i cleaned it.. just have this stupid code now

 

Maybe killed an O2 sensor?

 

Took my laptop out today to look at the live sensor data and the ses went off (good timing lol) I did see that it had started throwing the lean code for the other side but as of now they are both gone..

 

Ok ses is back on and heres what i found.. my long term fuel trims are pegged at +25% if i unplug the maf they drop slowly and stop at about +15% which is still high but better.. so im definately looking at a bad maf. Correct?

 

Its not the maf.. just tried a new one with same results.. anybody have any ideas???

 

Found it.. turned out to be a vacuum leak.. the pcv hoses behind the intake were rotted. Ive got 'em temporarily patched and LTFT's dropped to +9 with STFT bouncing right around 0..