Thanks for the ideas you guys. well, I replaced the fuel filter. The car ran perfect until it was warm. When it warmed up it started idling really fast (1300 rpm in park and about 1000 in drive) and erratically. In park, it goes from 800 rpm to 1200 then down to about 600 then back to 800 and so on, and it has a rhythm to it--like it's being controlled. It also smokes for a longer period of time now when you start it up, the color of the smoke is gray/white and not blue. I drove down my street with my foot just barely pressing the throttle at about 30mph and like 1200 rpm, and the engine speed was still inconsistant--up down up down. Still just an idle problem??? I'm gonna take out the IAC valve anyway and see if it's dirty, and then check the EGR system's vacuum.

Previously I forgot to mention that the car is pinging quite a bit when you accelerate and after every upshift. I use 88 octane chevron, and when I put 91 in nothing changed.

Oh yeah...the previous owner said he just did a tune up on the car before he bought his mustang. He was trying to fix the problem himself. I forgot to mention that when I bought the car, two of the vacuum hoses had huge cracks in them, and the car was running rough. I replaced them, and then the car ran smooth but erratically. Who knows how long those hoses were sucking air in. Could that have caused some major damage?

thanx again--I'm very determined to solve the mystery!!
white80zred89rs

 

Sounds like your egr port is pluged. That normally means a lot of pinging. Take it off and check. If thats not it then you've just eliminated one more potential problem. It does sound egr related though.

Steve

Edit: I just read your other post about the same topic. If you're absolutly certain that it's not the egr or a plugged egr port then I would say that it may be ecm related. You might also want to check your map sensor too.