i started this thread on modded mustangs, but wasn't getting much help so I am pasting it here:
Hi, I have a 1993 2.3L Mustang that is having some behavioral "issues" and I am having a hard time self Diagnosing, so I decided to see if anyone can help.
as soon as I start the car it will idle at 1500 RPMs for about 10 seconds, then goes down to 1200 for about 30 seconds, after that it will randomly begin idling pretty erratically anywhere from 900 to about 1200 RPMs. Then after driving it around for 10-15 mins, If I come to a stop (still engaged in drive) it will idle really erratically between 500-900 RPMs. if you shift back into Neutral it revs less erratically generally between 900 and 1200 RPMs again. (Generally for fear of it dying, I lightly rev the engine in neutral at lights)
I'm not really sure what the problem is... A while back (2 years) it had quite the opposite problem with the inability to idle, it would constantly stay between 2000 and 3000 RPMs... but after cleaning the IAC Valve, it stopped and acted normal ever since.
idle.wmv - YouTube Here is a video I took of it idling, kinda tough to capture the idle on video but if you look at the Tensioner pulley, you can see it acting up...
Any help would be greatly appreciated.
**Added about a day later**
I have tried resetting the computer on a couple of occasions, it would do a bit better for 10-15 mins until it "relearned" the bad Idle...
I cleaned the IAC again today with little change, and here's a video of the Tachometer after it was warmed up from driving across town to Autozone. It died on me as I was pulling in... so I parked it and took this with my cell... it was freaking out much more severely. (in park and AC/Heat off)After it warmed up[/url