my code is PO171. i have cleaned my MAF as said on http://contour.org/mods/mods.php?s=howto&displayid=36 ,changed both O2's, change the air filter. what else could be my prob? 96 2.0L

note this is the 4th time in 6 mounths it has come on with the same code

I searched that code on contour.org relating to a zetec. In addition to the dirty MAF and O2 sensors, it looks like it could be caused by a vacuum leak.

what kind of leak, internal? because i dont hear a sucking noise.

First clean the MAF censor.

or
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=zetecmaint&Number=755510&Forum=All_Forums&Words=19676&Match=Username&Searchpage=1&Limit=25&Old=allposts&Main=755510&Search=true#Post755510

my old post, have fun removing it as it's a common problem with these cars. Mines been on forever and I've changed everything but still no luck.

i did cleaned the MAF.

It could be a very small vacuum leak, perhaps around the pcv system or somewhere after the MAF. somehow, i bet unmetered air is getting into the engine so its not being picked up by the MAF and its running lean.

i did cleaned the MAF.
Any luck with the 171 code. I just ran across one with the same problem and have checked all over the intake with no luck. With no other codes showing up and have run on the diagnostics computer and all related sensors are operating within their allowable ranges this is turning into a real pain. Hopefully someone has an answer if this is a common problem. I guess it just another one of those ford things huh?