High RPM problem

[cosmo244]

Hello all, new to the forum. I am having some major rpm problems, ok I'll try to keep this brief. I got my comanche a little more than 1 year ago. This rpm problem comes and goes with the weather it seams. Dead of winter its fine but spring summer and fall lots of problems. I never have any problems getting started but 1 in 3 times the rpm shoots up to nearly 4 grand. Some times it will fall to normal in a few seconds but usually have to turn it off and restart it sometimes 2 or 3 times before it corrects itself. Every now and again it will start fine but after about a mile of driving it climbs up to about 1500 rpms and dosent go down untill I shut if off agian. Had a mechanic test the TPS and he said it was fine.....could he have been wrong? Maybe the IAC.....any advice will be appreciated.

[ejndssn]

this appears to be the same problem i have had in the past with my 89 MJ and once i replace the egr valve this problem went away. you may want to look into this and see if yours is in need of replacement. hope this helps

[DirtyComanche]

My cherokee does that if you park it in the sun.

 

 

Fires up and goes to 3 grand and stays there. Luckily the AW4 is tough and can handle being neutral dropped from that high of rpm.

[comanche-man22]

my truck does that too but not as often as you said...and yeah turning it off then on again like 2 or 3 times makes it stop for awhile...i have no clue what it could be. :roll:

[XJ Maki]

mine did it too for a while...it magically stopped on it's own

 

I think it was the TPS, I never had any luck turning it of - on again but whenever it happened I popped the hood and wiggled the TPS a little and it would settle right down. :dunno:

[Twisty]

Mine does it too!! I hate it, and it drives me nuts. I'm hoping it will go away.

[whowey]

I had the same problem....

 

Did it when it was cold. You could turn it off, turn it back on it would be fine. Then it would do it again. Tested the TPS, according to the FSM it was good.

 

I just lived with it(used to shut the MJ off at intersections, I have a manual, so I just used higher gears to control the RPM on the street). Finally it gave out and went to 3-4k all the time. It was a bad TPS.

 

 

EDITED for spelling.(Damn, I hate my kids' computer)

[offroader461]

i have the same problem but mine happens only every so often now...

 

i replace the TPS, IAC, MAP, and EGR to no avail....adjusted the TPS back to factory specs and every so often it will do it...i pop the hood and unplug the IAC and TPS and flick the thottle real quick..plug them back in and viola...all gone.

 

i just live with mine now :roll:

[Eagle]

I believe it's caused by a dirty IAC. The TPS may also play into it. I have had it several times on the '88 XJ, which is now up to 266,000+ miles. I've actually never cleaned or serviced either the TPS or the IAC. Whenever the high idle on startup starts to come back, I dump a couple of bottles of injector cleaner into the tank and that seems to cure it for another 6 or 8 months.

[attaboybob]

it must be caused by a combination of things.

I replaced the IAC and it helped.

until....it got cold. Then it did it a few times.

but, not as often. and, if I turn it off and start it,

it'll fix itself quicker. or, so it seems.

 

BOB