I have a 89 that I just got running today and when it's idling the engine "pulsates." It revs up and down, but only in idle. A friend of mine thinks it might be the throttle position sensor, but isn't sure. Anyone have any ideas?

 

How many RPM's is it pulsing? I don't know the '89. Does the '89 have EFI for a carb? V6, I6, or 4 cylinder? T

 

It's a 4 cyl with EFI. There's no tachometer, but best guess is 800 rpm on the low side of the pulse, and 2000 on the high side.

 

I have a problem where my AC shuts off when the engine idles while in gear. Apparently the RPMs are too low. The AC runs fine while idleing while in Park or Neutral. I had them raise the idle setting, however, then when it idled while in Park or Neutral, the engine would hunt between 900 and 1400 rpms. They adjusted it back down so it doesn't hunt, but my AC doesn't work.

 

I would check for any vacume leaks first this can cause that problem.