idle is too fast

[oldcat]

I want to know if I can get my 2.9 to idle at 500 RPMs cold and hot both? It was idling at 750 warm/ in drive and 1,000 plus cold. I sprayed out the idle speed control valve. Still the same. So I pulled the wires off the ISC and adjusted the throttle to 500 RPMs cold/neutral but when it's warm it runs at 700 RPM in drive.

 

[holyford86]

spec is 800 rpm warm idle in park when its cold its going to run at a higher rpm because more fuel is getting sprayed in there. The screw on the throttle body is for setting the TPS baseline it has nothing to do with idle speed. The procedure for setting the baseline is this: run the engine up to normal operating temp, shut it off and unplug the IAC restart the engine and run it at 2500 rpm for 30 seconds (you may need to depress the accelerator a little bit to get it to start), let off the pedal and adjust the idle speed to 700 RPM, shut the truck off and then restart it, run it at 2500 rpm for 30 seconds and recheck to verify that the speed stayed at 700 RPM. Shut the truck off and plug the IAC back in. the idle will jump up some but it is computer controlled and adjusting it to where you think it should be will mess with the computer and make it run poorly, the idle is non adjustable. The computer will run it where it likes to.

 

[low_five]

you will never get it to idle at 500 rpm. every little thing you can change, the computer will outflank you and ramp the idle back up to 800 or 850, depending on which transmission you have.

 

[74bronco2]

What and were is the IAC? My idle is staying at 2000 to 2500 put new air cleaner and ignition parts.

 

[The Fox]

It is on the passenger side of the intake manifold. It is the only thing that is on the manifold other then vacuum lines. The Idle Air Bypass(Controller) is used because the throttle plate closes air off completely in the idle position. Thus you need a way to get air into the intake.
Nick

 

[UnderMedikated]

Rangers seem to idle wierd and waste fuel. My 88 2.9 does the same. You start it and it races for a bit then it idles down around 800-850RPM. It does it when it's cold or hot out. I may need to replace all the engine sensors instead of 3/4 of them-LOL/NOT!