Strange low idle issue

[D M]

Where were meter probes touching when you measured the battery voltage. On the connectors or were you measuring from the battery posts themselves inside their connectors?

from the battery posts themselves

 

[Jerry Bransford]

from the battery posts themselves

Ok thank you. I asked where you measured the voltage because a battery can show 12.6v at the posts even when there's a problem with a bad/dirty/corroded/loose battery connection.

Your problems can easily be caused by a bad connection at the battery posts. You might also be able to see 12.6 on the connectors if they're in great condition but maybe not and they can also show 12.6v until there's a load on them which can drop the voltage the Jeep is getting. Sometimes significantly.

However not much has been proven here other than your battery is fully charged. What I'd do now is remove both connectors and wire brush both the posts and the inside of the connectors. A battery brush makes that job a heck of a lot easier since they include both a male side for the connectors and female side for the posts. Get them bright and shiny clean and see if that helps with your issues. I've had several problems over the years which were ultimately found to have been caused by a bad battery connection.

 

[Fonz54]

I cant seem to pinpoint my problem here. 2001 with a rebuilt 4.0, NV3550, progressively gotten worse these past weeks. I go to start it up, and the rpms go straight to 750, it used to go to 1200 and fall to 750 now it goes straight to it. It got worse, Rpms getting lower and lower each time. Now it will do that sluggish startup and fall to around 250 rpms and barely stay alive. When I drive it around and go to shift my rpms fall so fast its almost like someones killing the motor and it makes my shifts really clunky(if that makes sense). But heres the catch, its not 100% problematic, sometimes it will start normally and idle normaly(rarely) but now it just bogs down under 500 rpm and I have that issue when I push in the clutch. I put new spark plugs when I rebuilt the motor I tried jerry's trick using 1/3 can of throttle body cleaner into the IAC, took it out and cleaned it too. Im not throwing any codes. What am I missing here?!

On my 2006 Commander with the small V8 I had a very similar problem. Based on threads I read on the Commander Forum I replaced the IAC. All good for about two weeks and started doing the same crap again. Changed the TPS and voila that did the trick.

 

[D M]

Well I just ordered a mopar IAC since it appears the previous owner had a random one installed. Hoping this will do the trick