EDIT: if you dont want to read all that crap.... both banks lean. erradic idle when cold (to almost stalling out) but fine when just a little warm. changed TPS, ECT sensor, IAC valve, fuel filter, MAF (twice), both o2 sensors. no change. I recently bought a 2000 ford explorer and its driving me nuts. I bought it used but from a dealer, sort of thinking it would be more likely to be problem free since I usually buy from private party sellers and have to figure out why they sold it and fix it. unfortunately that backfired. anyway day after I drove it away, the CEL comes on. bring it to autozone for the reader and the codes are : right and left banks lean, emmissions system error, and random misfire. brought it back to the dealer I bought it from and he says its most likely an intake seal leak, so he changed that and ripped me off for an hour labor. (In CT they dont have to warranty any vehicle over 7 years old) so he says its all set and running great and come pick it up. CEL comes on, on my way home from there, and I kinda figure this guy is just gonna keep ripping me off so I decided I'd try to fix it myself from there. symptoms BTW are: running like crap from a completely cold start. drops from 1500 or so rpm's to 500 and about to stall, then way back up and repeats over and over till warm, then its fine. (the guy had it all warmed up when I went to look at it so I wouldn't notice the erradic idle.) so I get the same codes and start with the mass air sensor, tried cleaning it first but that didn't work and the sensor wires looked a little pitted and whatnot so I thought it was a good guess and got a new one. no difference. next I tried the tps since it was cheap and easy and sort of made sense. no difference but one of these did take care of the random misfire and emmissions codes, all thats left is the lean codes. next went with the ECT sensor since the problem is only when its cold. no dif. then tried IACV. no dif. Btw also sprayed all around looking for vacuum leaks and couldn't find any. actually did that first. also tried replacing the fuel filter since its cheap and easy. nothing there. gave up and brought it to a local garage, who's first thought was whatever the emmissions problem was had messed up both o2 sensors, which made sense. he tested them and said the readings were all out of whack and so we changed those. nothing. he was convinced the mass air sensor was still bad even though brand new, and thought it ran better with it unplugged (different yes but not better) so since I had the year warranty on that I swapped it for a new one for nothing. no diff. (and yes cleared all codes after changing that) lots of people also say maybe the gas cap. I doubt that would cause idleing issues but ok since the mustang is the same I just swapped them. no difference. out of ideas and running out of patience. anyone got anything for me?