Hello, I have a 1989 4runner that at 1300rpm - 2600 rpm will not hold a steady rpm. The engine surges , its like a kill switch is being pushed ,the rpms drop to about 1200 rpm then they climb back up to 1300- plus then it does it again. The engine idles fine at 1000 rpm and will rev till 1300rpm but it starts suging till 2600 rpm then will rev out to red line just fine. The engine will hold a steady rpm at 1000 - 1200 rpm and 2700 - red line . I can not get the truck smogged because it can not hold 2000 rpm for the high idle part of the test. I have replaced the cap and rotor and checked the distributor for play . I have checked for vac leaks and found none. Could it be the IACV ,TPS or the MAF ? Where is the IACV located ? Any ideas ?

Thank You

RLG

Which engine? Your other possibles include a head gasket.
How long have you had this truck? Any recent maintenance?

I am sorry it is the 3.0L v6. I have had the truck for about 5 months. I have been restoring the truck as a project and now I am finished( new paint ,windshield,stires and wheels ect. The motors compression is good so I dont think its a head gasket and the antifreeze level is full and no bubbles with the cap off and engine running.