ok bought this 93 zj 4.0 inline six runs great but i charged the ac an the fun begain the oil pressure went crazy it idles at a normal 20 psi if u touch the gas it goes to 80 if u drive it it bounces from 50 to 80 at 50mph when its at 80 and u mash the gas it will drop to 50 let off the gas back to 80 i changed the oil and filter no change any ideas

 

Sounds like a bad oil sending unit.

 

AC have nothing to do with. Your oil pump my be going out or bad sender unit.

 

Guess i should replace both to be on the safe side

 

i'd replace the sender first since i'ts quick and cheap. if the problem continues you could get a mechanical gauge and screw it into the oil pressure sender port to determine weither the problem is in the engine or the guage circuit.