Hi All,
This forum has been a great help so far!

I have a 2004 A4 1.8T (FWD) and I've been trying to figure out why I keep seeing code P0171.

Last week I got P0300, P0301, & P0302 so I replaced all spark plugs, which were really bad, and I replaced the 4 coil packs.

After doing that, I cleared the codes but the next day the CEL came on and I got code P0171. I checked all of the hoses for vacuum leaks, but I couldn't find anything.

I put a vacuum gauge on the intake manifold and it shows 18 ins of vacuum at idle. Is this a good reading for this engine?

Thanks for all your help!