[turbointhailand]

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.

Basically...

as soon as I start the car it will idle at 2000 RPMs for about 10 seconds, then goes down to 1500 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.

Video of Erratic Idle Here is a video I took of it idling, kinda tough to capture the idle on video but if you look at the Tensoner pulley, you can see it acting up...

Any help would be greatly appreciated.

[OHC230]

Good video it helps in this case. Before you start tearing into anything, disconnect the plug to the IAC while the engine is running and reset the base idle speed to 850 RPM. From the video, I'm almost thinking that it's not related to the IAC though, it sounds like the crank sensor signal is being interrupted or a coil pack is dying. Have you tried disconnecting the battery to reset the computer?

[turbointhailand]

Thanks for the post --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, and its off right now so I can put it back on in the morning... now I've never had to set an Idle before, I'm assuming you mean with the Idle Screw on the Intake manifold (I might be wrong) if you could give me a quick walk-through that would be most helpful.

Also heres a video of the Tach after it was warmed up from driving accross 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

After it warmed up

[tcl1103]

I'm no ford guru that would be ohc, but take a look at your mas. When i bought my 90 i got it for cheap because it ran like that it turned out to be a vacum issue more specifically the vacum line to the map sensor. However, I would point the finger at i vacum leak first.

[TurboLX]

sounds like the mass air