Hi all i am new to the forum and this is my first post so excuse me if I haven't learned the ways of everyone around here.
I am yet again having issues with my idle.
Previously I had a low idle issue that required throttle to keep it alive until you were moving then would operate fine it would go away after warmup.
That problem was fixed about 25k ago.
I have in the past replaced my iac and cps.
Had my intake manifold removed and cleaned.

Now more often then not I have a high idle issue that is really starting to worry me that it will be putting undue strain on the drivline.
My out of gear idle can be as high as 1500rpm. It is really random and I have yet to define a pattern. It occassionally is a normal 600ish rpm idle but that is now more a rarity. The only other engine related problem that I don't think could be a contributing issue is I have a bad O2 sensor that is still in place but has been disconected since the wires freyed. I just haven't gotten around to replacing it.

I am starting to think that it is an issue with the idle control stepper motor.

I haven't messed with it yet and wanted to see what everyone thinks here first.

 

When was your last tune up? Plugs, wires, cap and rotor should be replaced every 30k. Your o2 sensor could be contributing to it, i'd start with replacing that. Clean the throttle body. Disconnect and clean the iac (that largely controls the RPMs). Also, test your Throttle Position Sensor to make sure it is working properly, that may have something to do with it.

Is it throwing any codes? That could help you diagnose it.

 

Ok so forgot to add vehicle info.
It's a 2000 cherokee classic with 205k on the OD
So it's EFI 4.0 and the plugs and wires are about a year and a half and 30k old

 

the only code is for the O2 sensor

 

Okay well you're due for a tune up. And also get that o2 sensor replaced. I seem to remember hearing of someone's idle and such getting twacked with a bad o2 sensor. So do that with a new NTK one, XJs do well with those, not a crappy Bosch

 

sounds goodwill give that a try. I wouldn't have thought the O2 sensor would tweek the idle like that

 

Well the 02 sensor and plugs mostly fixed the problem occasionally acts up still but much better than before. Hasn't gone above1250 idle since and usually stays under 1000 now. Guess i must have an iffy AIC or TPS still. How do I test them I have no codes now since the O2 was replaced if anyone knows. They have lifetime warranties on them since I replaced them both not long ago.

Thanks for the help and my torque converter does too.