Won't Idle Correctly After Attempted Repair-What Next
I have a 2000 Jeep Cherokee 4.0L ( XJ ) limited trim. It will not idle correctly. below the regular RPM or above..... i replaced the idle position sensor and had the IAC system reset by a friend who is a mechanic. ( idle sensor was to blame, to keep my question short). Everything seemed to be quite fine having done this yesterday. Even seemed to run better/stronger
Until this mourning when it would not idle at all.... until i started and held the gas down above idle speed for about 60seconds. Also does not idle at a consistent speed and occasionally idles rough.
I will be doing a tune up over the weekend since it is due, which is fairly easy with no plug wires etc just the ignition pack over the plugs.
I am not sure if this will help with my current problem since the computer should correct within reason for any ignition timing if i had bad plugs? yea?
If anyone has any ideas? let me know. If i had a bad part in the ignition system it would throw a code? and the check engine light has yet to come on and everything checked out ok just yesterday.
Also make sure that you check for vacuum leaks. Mist the engine compartment with some WD40 around the vacuum lines and see if the RPM increases, if so you know you have a leak. The other thing to look for is the Throttle Position Sensor (it is located right next to the IAC in the throttle body). When it goes bad it will think the throttle plate is either to closed or to open. Of course, a bad (or going bad) fuel pump can give you the same symptoms as well.
Another thing to check, if your truck has it, is your IAC (idle air controller). My truck actually decided to spring the same problem you're having (though I have an engine light on). It was running super rough (I could even feel a cylinder misfiring) and didn't like starting. I swapped the plugs and used fuel system cleaner and it runs almost perfect now. It just doesnt like idling when cold. (Sound somewhat similar to yours?)
I've been told that the IAC can be the cause of this. If the truck runs fine except for your idle, check the IAC...that's my next step!