Idle problems
 

hi guys.I have a question for you rotary wizards. Been trying to chase this problem down for a long time. When my car warms up to operating temperature, if it's just idling it will drop down to 200-400 rpm then go back up. People are saying it could be vacuum leak, tps, iac, or thermostat. What Should I try first and is there anyone with other solutions.

If you're driving in cooler weather does it purr like a kitten? A bad water thermosensor will cause a fixed input of 80C. If you pull code 09 that is your problem.

I had a similar problem on my 87 t2, my car actually died once it warmed up(always had to give gas to keep it running). Turned out to be a bad TPS. I connected an ohm meter to it, and swept the throttle, found a dead spot. You should fist warm up the car to operating temperature, and then check TPS, It should be 1k ohms. or 1v. Sweep the throttle and make sure there is no dead spot in the TPS. I would start with that, or spray brake cleaner around the engine to hear if RPM changes for a vacuum leak.

Could be BAC failing.

Idle Problems
 

I had a very similar problem and it was a bad BAC valve, replaced it and that took care of the problem.