I have a ZJ 1996 Jeep Grand Cherokee Laredo 4.0L.
It idles to low (gauge has 2 marks between 0 and 1 and it sits slightly below the top mark while idling). I have to come to a stop gradually, letting the transmission go into 1st gear or I am afraid the engine might stall. Other then that it seems to run fine.
The only codes that show up on the odometer are 12 and 55.
I have disconnected the battery, removed the throttle body, removed the mass airflow sensor from the throttle body, removed the idle air control from the throttle body idle air control housing, removed the throttle body idle air control housing from the throttle body, removed the throttle body air control plate, cleaned the throttle body, cleaned the throttle body idle air control housing, cleaned the idle air control, cleaned the throttle body air control plate, reassembled all parts back onto the throttle body, reattached the throttle body back onto the intake manifold using a new gasket.
There was carbon buildup, on the throttle body below the air control plate, on the underneath side of the air control plate, on the throttle body idle air control housing, and on the idle air control itself. All carbon buildup was removed (the carbon buildup on the idle air control pintle was removed very carefully).
I still have the same problem!
Do you think this could be a bad IAC (idle air control) even though no codes appear on the odometer display? How do you test the IAC? Can you remove the IAC, while keeping it connected, and then turn the ignition key half way to determine if the IAC will move the pintle?
What about the mass air sensor? Can it be cleaned? Is there a way to test it?
P.S. Will a scan tool show additional codes even when the odometer doesn't show any codes?