Hi, I have a 1997 Ford Ranger with the 4.0L V6 and the 5 speed automatic transmission, 183K miles. When I am at a stop the truck with no AC on will be at 500 rpm sometimes dipping below that. When the AC compressor comes in it goes back to the normal 700 rpm. Every time the compressor turns off and the rpm drops I feel the truck lurch. It also lurches forward if the rpm is low and I hit the gas and sometimes that will cause it to stall out, or turning into a parking space will also cause it to stall. I've looked for a vacuum leak didn't see anywhere in particular where the smoke was being sucked in. Also the IAC has been replaced didn't fix the issue. Fuel filter has been replaced and fuel pressure is at spec. Any help is appreciated
-Evan

 

IAC valves must be Motorcraft or Hitachi. I've read that other brands are incompatible.

How thoroughly did you check? Perhaps using a spray can of brake cleaner along gasket-sealed edges etc. is necessary.
I don't know if your OHV has the same L-shaped pipe from its PCV as the SOHC does, but check all of that stuff too.

During this search, give your tank a dose of Techron before a stint of local driving. Any engine with your miles might have dirty injectors.
Make sure the MAF sensor is clean.
Check the throttle body for a "gunked up" condition.