I finally got back to my 89 3.0 4Runner project. I fired it up and it is idling at about 1300RPM. It stays the same. The engine is equipped with headers, cat back exhaust & a Downey air intake setup. There doesn't seem to be any intake or exhaust leaks. Engine is supposedly a dealer installed factory replacement. Any ideas on what could cause such high idle speeds?

 

It idled fine, now it suddenly doesn't? Correct?

Then here's what the FSM checklist says:

1. Accelerator Pedal Link
2. Dash Pot
3. ?(missing from the list)
4. Engine Coolant Temp Sensor Circuit
5. Idle Speed Control Valve
6. Intake Air Temp. Sensor Circuit
7. Throttle Position Sensor Circuit
8. A/C Signal Circuit
9. PNP(Park/Neutral Position Switch)Signal Circuit
10. Injectors
11. Cold Start System
12. Engine Control Module

http://personal.utulsa.edu/~nathan-b...63troubles.pdf
http://personal.utulsa.edu/~nathan-buchanan/93fsm/

 

mine ended up being the intake plenum gasket

 

I won't say suddenly because it hasn't been run in a year, but when I bought it it idled fine. I will start on your list. Thanks