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Discussion Starter · #1 ·
Does anyone know how the solniod on the inboard side of the throttle body works on a 91 4.0 cherokee!
Haveing some idle problems have removed and cleaned this unit and it idles somewhat better but not sure as its working right yet?
Was stalling! It doesent stall now ,but it dosen't idle down slowly like it used to! It just drops to 500-600 rpms like a stone?

 
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Discussion Starter · #2 ·
i suspect that it is probably the throttle body sensor. they will cause the idle to go crazy and then level out and then go crazy again.

 
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Discussion Starter · #3 ·
The thing you describe sounds like the IAC (Idle Air Controller). It should be cleaned every 15K miles or so along with the throttle body bore. The engine controller uses this to control the amount of air bypassing the throttle blade thereby controlling the idle speed. You need a diagnostic readout box to actuate and test this unit. They are pretty reliable though and problems usually are traced to a loose terminal or water in the connector. There is an aftermarket tool that you can use to actuate the IAC motor, but it is expensive and can be hard to find other than off of a Snap-On, Mac, Matco or Cornwell tool truck. The normal range of idle speed is 750-800 for the 4.0l if the throttle body is clean. Usually the PCM will adjust for the normal oil residue buildup in the throttle body, but if you disconnect the battery, or the battery dies, the PCM goes back to its' base setting and you will have stalling when coming to an idle or when starting. Cleaning it with sensor safe throttle body cleaner/carb spray will prevent this problem. Hope this answers your questions, good luck.

 
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