Hello Everyone,

I apologize that my first post has to be about an issue, but I'm at wits end! I recently purchased a 96 Montero SR OBDII and shortly thereafter I discovered a strange (to me) problem.

So what happens is that at some point in driving the car it will begin to idle between 1.5 to 2K. The idle might be at 2K and drop slowly to 1.5K, then jump to 2K and repeat. It doesn't matter if the car is in gear or parked. HOWEVER, if I turn on the AC, it idles perfectly near 800K.

But what I noticed on Saturday was that for part of the day the idle was fine. But when the idle was ok, sometimes the car would crank but not start (after driving and parking for anywhere from 15 min to 1 hour). BUT, if I turn on the AC prior to starting the car, it would start fine!

On a side note (not sure if this is normal, and if not, related), If I'm driving at 45 or 50MPH, and lift off the throttle in 4th gear (its an auto), I see the revs fall from 2k to maybe 1,250, then then go back up to 2K and repeat. Not sure if it is normal or not.

So my research lead me to possibly a bad IAC. I bought a used one from eBay. The unit in my car is the beige unit and the eBay unit was the black one (newer unit, slightly smaller). After installing it, I noticed no difference. If anything it seemed worse. So I took it off.

Now I have no idea what is going on. Any help would be greatly appreciated.

BTW: No check-engine light at anytime during these issues.