1989 Cherokee 4.0 rough idle in very specific circumstances?

Idle Air Control Sensor

Throttle Position Sensor

Crankshaft Position Sensor

Go to a local parts shop, buy each one in that order and replace it, once you find the cure return the other two. They will accept it assuming you kept it in new clean condition and didn't have it more than a few hours at most.

My money is on your IAC though.

Hmmm problematical to assert, yet enable's ask greater questions, idles effective in independent or park yet no longer in force, Vacuum leak may be the finest to get rid of. whilst, idling take a can of carb or choke cleanser and spray your vacuum traces at quite a few places listening for a transformation in RPM. the assumption is that in case you have a leak or broken or broken vacuum line it quite is going to suck in the choke cleanser and you will hear a transformation in the rpm. you additionally can "t" a vacuum guage in numerous places to verify your vacuum looks good. With this out of ways, we circulate too finding on the plugs, put in force enable run for somewhat (in case you may desire to positioned your foot on the gasoline an injury thats effective) 2 or 3 minutes. Then close off and pull plugs, verify out plug for lean or rich burning subject, or a achievable moist plug, which could be no burn in any respect. If rich, too lots gasoline, have been given to sensors and ecu, injectors and so forth., If lean, visit 02 sensor. If moist, visit spark. So as quickly as you artwork which thank you to circulate (lean or rich gasoline) or (good or undesirable spark) you may desire to besides throw in a compression try just to rule out the air factor (air, gasoline, spark 3 issues you elect for suitable working engine) Compression could desire to be approximately one hundred fifty-200 interior 10 % of eachother in the time of all cyliners. in case you have this then you definately could desire to artwork on spark and gasoline. Off hand, working tough at idle, sounds like a gasoline subject, your the two attending to lots or to little, the laptop sends gasoline (opens injectors) in accordance to sensor indicators,(o2, map, mas, mat, coolant temp, tps, cps, and so forth..) at this factor, pull codes in reminiscence for a defective section, and then decide which sensor is featuring undesirable information to the laptop. in case you have a concern while heat yet no longer chilly, or once you first start up it and you haven't any longer replaced the 02 in 50-60k miles evaluate a sparkling 02 sensor (basically good for type of 60k) in any different case good success.