94 GSR Idle problem

My g2 died so i got a nice 94 GS-R… im having a problem with my idle0when i start the car the idle goes up to 3k then after a few seconds it drops to 1.5 and then goes up and down beetween 1.5 and 2.5. when the car heats up the problem dies down a little and then whne the car is hot and i turn the AC on the idle stops bouncing and stays at 2K. Anyone got an i dea whats causeing this?? also whats the best oil for a GSR gen 3 with 10000K miles? thanks alot …

help

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