My jeep runs great everywhere but at idle. At idle it feels and sounds like its missing. I have checked plugs, wires, cap and rotor. All good. Ideas welcomed.

Flash

 

IAC controls idle speed only. If the idle speed is ok then the IAC is doing it's job.

 

try cleaning IAC,throtle body. check for vacuum leaks, plug/restricted exhaust. check wires with VOM. dirty fuel injectors. there's a couple hours of things to do.

 

Clean tb and iac if that dont do it check wires make sure iac signal is good then if ur wires are good replace iac

 

What's got me baffled is it is only running rough at idle. Hmmmm?

Thanks,

Flash

 

Try cleaning TB and all sensors and try seafoam and when was the last tune up done on it?

 

You could have a valve not sealing completely. Worn, carbon...etc.
Timing chain could be stretched. Lots of things can cause a rough idle.
Have you done a cylinder balance test?
What year is your rig?

 

Idle Air Control Valve.. clean it, but don't put any 'twist' on the pintle. I think I read that's bad. You might also spray some starting fluid around the engine to look for vacuum leak

 

IAC only sets idle speed.

Miss only at idle says vacuum leak.

 

Plugs, wires, cap and rotor are due to be replaced every 30,000 miles. When was this last done?

 

Do a compression test and a cylinder leak down test if you can, you may have a weak cylinder. How many miles on this rig?

 

150k well maintained miles.

Flash

 

iac only keeps engine running when another engine component takes power from engine.iac gives back missing rpm's /decarb your engine & start over -1 take A bottle of cheap fuel injection cleaner 2.take powerbooster vacuum off 3 KEEP ENGINE RUNNING !!!!!!!!!IT WILL TRY TO DIE THE WHOLE TIME (USE LINKAGE ON TB FLOOORED!- LIKE YOUR TRYING TO BLOW IT-LET IT SUCK FUEL INJ. BOTTLE DRY.4 STOP WAIT 30 MINS 5 FILL BOTTLE W/ WATER REPEAT 3 PUT VACUUM BACK ON DRIVE ---"notice HUGE difference" will increase horsepower & gas you just nocked all carbon safely from comb cham and pistons!

check 02 sensor

 

there is no iac @ idle just as there's no egr @ idle ...take egr off if car runs replace

 

Well, I think I found it. Only 100 psi in cylinder #1. Still runs good, just has rough idle. Looks like a valve job is in my future. Bummer.

Flash