Idle question

I just got my runner started and it sounds great. How ever it will idle at very different speeds for a little and then switch speeds again. For example i start it and it runs at about 1500 for 30 seconds then it will drop to 200-300 for 30 seconds. Almost to the point of dying. And then jump back up to 1500. Anyone know what’s up. No dash lights are on.

 

I'm no big expert, but it sounds like an air leak on the intake side. I had somewhat similar symptoms, only much worse, and it was a torn plenum gasket.

 

Thanks, doesn’t matter anyways. She blew a head gasket