2000 Cherokee 4.0 85,000 miles

Problem: Idle bounces between 400-500 rpm, whether cold or warm, runs/drives great.

Codes: none.

Tried: new iac/plugs, cleaned throttle body (wasn't that dirty), sea foam (via fuel tank and throttle body).

Other: Jeep did sit unstarted for nearly 2 years as I was overseas.

Any thoughts would be appreciated guys, I just don't want to throw money at the problem.

 

Does it want to die or stumble at all? My '99 idles around 500-600 acording to the tach and doesn't miss or stumble at all. I figured that's where it should be.

 

I believe the 4.0 idle should be anywhere from 750-900 rpm. It doesn't stumble or act like it's going to die. The idle was approximately 900rpm before it sat untouched from what I remember. Plus it bounces from 400-500, not a very steady idle.

 

TPS adjustment sir......shop manual has procedure, or you can bring to a jeep specialist and they can tune it in.(this will bring idle speed up some)

also, check ALL hoses for cracks, leaks, frayed, split, etc....espcially those lil tiny hard plastic ones,,,like that go to the MAP sensor and stuff. (use inspection type mirror and strong flashlight to see back sides of those small hoses).

there is some tweaking that can me done on it.

good luck sir!

cpnwrench

 

rrrrrrrrrgh I hate when I mis-spell...

"there is some tweaking that can BE (not "me") done on it."


cpnwrench

 

Thanks for the advice cpnwrench. I will play with the tps sensor and replace if necessary. I was more afraid that the low idle would indicate a bigger issue.

I thought about the vacuum lines, but I don't notice any obvious hissing noises. But it can't hurt to take a closer look.

 

No adjustment on the TPS for 92 and up XJs.

 

Let us know what you find out!!!!!! Cuz' if I ever get this, I'd like to know right away...

also, just as a side-tease....and this might validate what I am thinking......

get on high speed road.... set cruise control on say 60 or 65. (if you have cruise that is).

if she starts accelerating rapidly, then its the TPS for sure...
(I know cuz' that happened to me).

anyway, be nice to know what you find!

cpnwrench

 

Yep, Busted, you are correct, but..............!!!!!!!

I found this "intoxicatingly" detailed link for the 2000 xj Throttle Position Sensor replacement, yadayadayada...........(meaning etc.,etc., etc.,)

go here:
http://www.jeepforum.com/forum/f13/t...01/index3.html

then find entry #36 and read down to entry #40

nice pics in there.........

cheers!

cpnwrench

 

Thanks for the response BustedBack. You of course are correct. Unadjustable. I'll need to replace tps, probably oem, to avoid any other issues.

Any good places on the web to pick up xj parts? For a tps or otherwise?

 

I checked the vacuum lines, appear to be in good shape. Everything is connected. No cracks etc.

I have also been on the highway, recently 2-3 weeks ago, used cc, 65mph+, 1.5-2 hours, nothing out of the ordinary. When I replaced the iac 6 months ago I looked into the tps, but assumed it wasn't the issue because I only have issues in park or at a stop...simply at idle, not during acceleration. At least the tps is not too expensive.

Once I replace I'll let you know if the issue is resolved. 400-500rpm is just too low.

 

Just replaced the tps...Jeep is running the same if not worse than before, no ck engine light.

Any thoughts?

 

Is it a Jeep OEM part? Ive had badluck with autozone parts, dont even get me started with those fools.

 

It is a pepboys tps. If it is defective would it throw a code? Even w/o a ck engine light? Guy at pepboys has a gc and he replaced his with the aftermarket. He said it worked fine.