Sometimes after the car is up to operatring temps and shut the motor off then restart it latter the motor still at operating temp it will rev to 3500 to 4500 RPM's then go down to 1000 RPM after a couple seconds WHY.

I dont have any vacume leaks the base Idle is set at 450 RPM's the Normal timiming set a 6 advance.

Most of the time in gear the Idle is at 650 to 700 RPM In gear it's a uto trans.

The motor not stock it a mild build it has a chip for the mods.

I dont remember the motor doing this before the rebuild from stock motor.

It will also surge when slowing down moving foward to a idle 650/700 Rpm's to 1000 Rpm's I think it's the TQ convertor the place that rebuild the trans screwed it up I still working getting anouther trans.

 

i have the same issue

 

I had a Spare MAF I swaped it out and adjusted the Volt of the TPS from .55 to .539

It runs much better I dont Idle as high any more during start up.