IDLE PROBLEM

[sjan]

My 99 runs great for months; Then all of a sudden it won't idle. If I keep my foot lightly on the accelerator to keep it from dieing when stopped, I can drive it, but it's a pain.
Then after 20 min or so it idles just fine. Then sometime later it happens again.
What all should I replace to hopefully fix this very intermitant problem.

 

[RichP]

Depending on how you drive several things, first if you are a pokey driver or one that drives short trips take it out on the interstate and run the piss out of it, that will clear out some carbon.
Other thing is every few months run some Chevron Techron fuel SYSTEM cleaner thru it and clean out the throttle body with a good de-carbonizer.
Also keep track of where you buy your gas, maybe one of your stations is cutting it with something.

 

[EMSJEEP]

hmmm...sounds like the problem I just posted about a few minutes ago....well, if nothing else, you're not alone
http://www.naxja.org/forum/showthread.php?t=914089

 

[Ecomike]

Do the 99's have an IAC on the throttle body?

If so it could be sticking intermitently.

If so it needs a mild cleaning and oiling.

Search the words "Idle Air Control Throttle Possition Sensor" in the OEM forum here for the usual suspects and many prior discusions and previously posted test procedures for these two parts.

There are many other less "Usual" but possible possibilities including wiring insulation partially breaking down in a number of control and sensor areas that can be intermitent (due to movement and /or moisture changing the leakage current and thus the symptoms) making it hard to diagnose. Loose corroded connectors, poor grounds, loose battery contacts, or a small amount of several of these all added together can cause week signals to the computer controller causing it miss adjust the idle.

With a 99 you should start with geting a computer scan (OBD-II) for computer error codes that might indicate the source of the trouble in a memory error code. Then get a multi meter and start checking signal voltages per an FSM or posted test data here in various threads for various sensors.

It may take days or weeks to find the problem and then five to 30 minutes to fix the problem.