[ShadeTree93]

What would cause my 93 RRC's RMP's to fluctuate? Its very mild and the truck does not want to die or anything but is was enough to cause the guy doing the smog test not be able to get a timing reading.

(did I just answer my own question? Do I adjust the timing? :think: )

 

[rover4x4]

Not timing, most likely the IACV (stepper motor) needs to be replace or there is a vacuum leak. Stepper motor is located in the back of the plenum its like a 1/1/16th size.

 

[stuart460]

clean out the throttle housing remove the idle valve and clean the housing refit the stepper motor ensure the engine is cold and run up to temp.ensure you have no air leaks or a fualty temp or afm as theses effect the idle but if all is ok proced with the next step
ensure you have no air con switched on, and no electrical loads.
connect a seperate tacho unit and clamp the black hose to the stepper motor housing the idle should fall to around 520rpm +/- 20 rpm if it is not then turn the alen key screw on the top of the plenum untill it idles at 520 then slowly remove the clamp and the idle should be 720 +/-50 rpm