I have a 95 2.5 5-speed, 2wd. I’ve been having a very puzzling issue, where if I pop it into neutral at any speed, my idle will hang around 1.5k and then drop down slowly to about 1k.

When I first got this thing, it would idle really high. It had the standard cluster in it, the one with the big gas gauge, and so I never knew what it was idling at.

I swapped in the sport cluster after I did my clutch and put in a transmission after my old one blew out, found out it was idling at about 1.3k Replaced some vacuum lines, the OCV line, intake and exhaust gasket, rocker cover and oil pan gasket, and brought my idle down to about 1.1k. Did my TPS, MAP sensor, and o2 sensor, and that brought my idle down to about 900.

Now back to the original issue.

My first guess was the TPS sensor. It would give me random voltages all across to full throttle when I back probed it, and no change. It would still idle at about 1.5k if I push the clutch in, go to neutral, and coast. It’ll start dropping eventually, and then when I come to a stop it drops down to about 1k. Almost like the transmissions not 100% in neutral.

I’ve also cleaned out my throttle body, and shook around the IAC, and I can hear it move somewhat. Didn’t have the little torx bits to remove it and clean it, but I tried to spray some cleaner in there. But then again, I don’t know if it’s the IAC hanging open and causing a high idle.

Anyone have some pointers on what to test/do next?

 

I would be suspicious of the IAC.

 

x2 get some torx bits and remove the IAC so you can clean the tip and passage out.

 

The IAC can be delicate/fragile. Definitely the first thing to look at when having idle speed issues

By saying yeah it is there and hooked up you might aswell be looking at a spark plug and assuming the condition of it without actually taking it out to inspect it.

 

https://www.cherokeeforum.com/f2/hig...riving-263538/



Been there. Replace the TPS. I know you already did. It's frustrating.

 

I usually preach testing before blindly replacing parts, and sounds like you did that with the TPS already. Verify it has a good ground too, as that will cause the sensor to read high and cause your symptoms. Ideally, you should go clean all the important grounds, especially where they all attach to the engine block. I think the 2.5 has the same bolt by the dipstick where lots of grounds converge?

Personally, I'm somewhat frugal and would probably buy a cheap non-mopar sensor, do a sanity check with a meter, and see if that fixes or changes the problem. It's easy enough to replace, that I'm not too worried about the quality or longevity, but I would start looking for a good deal on a mopar one expecting to need it in the near future. Critical parts or parts that are difficult to replace like bearings or could leave me stranded like the crank sensor, I really try to go with quality parts though.

 

I do too. But mine tested out fine. Every time I'd test it, it read good. The weird part about my TPS doing what it did was that it would start reading high after driving around a little. If you see those data logs, it would go to zero for the first 15-20 minutes of driving and then suddenly it wouldn't go below 15%. If I came to a stop and turned it off, the TPS would test out fine. The only way I found it was with that datalog.

I used an ELM327 Bluetooth adapter and an app called Car Scanner.

 

I don’t have OBD2. I have to use a voltmeter and back-probe **** and cycle the key 3 times and count the blinks of the CEL. No fun.

I’ll test the TPS again sometime when I get back to work, and i’ll also clean out the IAC and check the ground like someone said.

And as a side note, i’m not even sure how accurate my tach is. I got a sport cluster and swapped it in, and it sometimes jumps randomly. It says it’s idling at about 900-1k, but it really doesn’t sound like it.

 

I just wanted to update and say that a new IAC motor fixed a lot of issues. My idle is lower, it’s more consistent, and now when I push the clutch in, it actually goes down to idle and my gearshifts are more smooth. It still has a high-ish idle, but that’s because of a vacuum leak I can’t figure out how to fix yet.

I also should note that the spring inside of the the old IAC was stretched out to its max, and was about 3 times the length of the new one. It was 40 bucks and now it feels normal at idle

 

Congrats - those pesky things gum up and sometimes just carb cleaner will work. But it sounds like yours was due

 

I tried to clean it up. I let it sit in a vat of parts cleaner overnight, didn’t fix anything. I thought I heard somewhere that you can’t get the motor, but I found it at my work on a delivery service we have, and low and behold it fixed everything.

Only thing I didn’t like about it was that one of the holes was drilled wrong, so I had to hollow it out as much as possible to get the screw to fit right

 

Who made your replacement? I put a Standard brand starter motor on mine (available at O'Reilly's - one of the few good names still around) and it was plug and play at its best