Hello all!
I'm a Masshole, that loves German cars..Hawaya'z?? I drive a 2001 Audi A4 1.8t Quattro.. Just approaching 76k miles. Have had a CEL on for a month, or more. Auto Zone code P0171. A friends code I believe was P1128. I forget. Anyways, I've replaced as many vaccuum lines as possible.. I took the MAF sensor out and cleaned it, and the CEL stayed off for 350 miles.. It just popped back on last night. Same code... THis may sound stupid, but, I do asssume that the MAF sensor is my problem right there? The car still rides better than before it was cleaned... almost like a dream. Any input will help! Thanx!
Timmy Dyse

 

P0171 is a generic "system too lean" and P1128 is "long-term fuel trim too lean". MAF can create codes like that, as can vacuum leaks, but your primary O2 sensor (the one closest to the turbo) is the main determiner in fuel mixture. It's possible for it to be degrading and causing a poor mixture, without being bad enough to trip a CEL for an O2 sensor failure.

 

I had this same problem and i replaced all the vacume lines in my car as well. I still had the cel on. Ended up being a hole in my cat that was causing the o2 sensor to read to lean. Id check that as well. Good luck!

 

When I was getting P0171 in my 2001 it was a MAF, but as stated above check all possible avenues..

 

Thanx for rapid input! I will check everything! I thought I fixed it just by cleaning the MAF sensor, when the cel stayed off for 350 miles, when it wouldn't last more than 30 prior to the cleaning. I'll get it on a lift and inspect the cat, and just change the MAF sensor, and O2 sensor if that dosent' help. Thanx!

 

Whats the update? You figure it out yet?

 

Well, I took the MAF sensor out again, cleaned it more thouroughly, and the CEL went off by itself, and has stayed off for another 115 miles. I'm gunna' wait til' it comes on again.. knock on wood.. then replace it if it does.

 

Ok so the CEL has been going on and off after the MAF's last cleaning.. about 100 miles between each.. so I've replaced the MAF sensor.. Had the light reset, and I'm goin' 350 miled strong with no CEL.. Car rides great too..!! On the darker side.. All 4 of my center caps were stolen off of the wheels last night, or, the night before.. SOB! Figures...