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92 xj problems

J

jamesxjowner

NAXJA Forum User
Location
Oakhurst CA
i have a 92 xj with the 4.0. got in a finder binder a while back and had to replace the radiator, tranny cooler and bumper. well it ran fine then a week later the MAP sensor went out and now it will just idle up and up and wont drop. could this be a clogged EGR, bad TPS, MAP, or Mass air flow? or even a ECU? really want to get it on the road again soon so any help would be great
 
Intake leak that gets bigger as it warms up, vacuum leak, bad IAC, bad IAT (That was the one that drove me nuts!!!!!), or a BAD ground (oil dip stick location, or the hidden sensor grounds in the harness) that drifts and gets worse as the engine warms up.

Hint, check the voltages cold and hot, especially hot as the idle climbs and reaches peak idle rpm!!!
 
jamesxjowner said:
i have a 92 xj with the 4.0. got in a finder binder a while back and had to replace the radiator, tranny cooler and bumper. well it ran fine then a week later the MAP sensor went out and now it will just idle up and up and wont drop. could this be a clogged EGR, bad TPS, MAP, or Mass air flow? or even a ECU? really want to get it on the road again soon so any help would be great
Click to expand...

First off, reminder that this is 90, not a 92 jeep, so a bad ECU is not all likely. There is no MAF sensor on XJs.

EGR problem is possible!!!! Including a bad EGR diaphragm leaking vacuum!!! bad air manifold or coolant temp sensor is possible.

Most likely is a growing (but not yet located) vacuum leak while it warms up.

Vacuum can leak at the brake booster, the bottle in the bumper!!!!!, the hoses under the battery, leading to the bumper bottle, the AC vacuum lines, inside the cab and under the hood, the EGR, the egr solenoid, the MAP sensor to throttle body vacuum line and along the rear firewall, and at the throttle body and the I-manifold.

A bad Intake temp sensor will cause high idles too!!!! Ask me how I know!!:doh:

You say the grounds are good, but what data results did you get, how did you verify the grounds?

One other though is a an FPR diaphragm leak of gas into the vacuum lines, or leaking injectors, adding fuel, but that usually causes other issues too, like a flooded engine hard start.
 
ya i checked it with a gauge and everything well my buddy that owns a shop did. i never seen this bottle in the bumper that ur talking about. only bottles i seen r under the hood and stuff but ill check all those sensors and stuff but all the vacuum lines have been replaced and we hooked it u to a scope and found no leaks any where plus egr is brand new and all that.
 
How about the throttle body to the manifold? Make sure no leak, bad gasket, etc. there.

Can we assume that you have eliminated any and all mechanical issues with throttle linkage? I say that because my 87, which had a taste for variety, managed to provide high idle problems not only from a rusting accelerator pedal pivot, but later from a worn and binding bushing on the throttle linkage bell crank, in addition to the usual sticking IAC pintle and a just plain worn out throttle body. Every time I would replace one thing, another would pop up.

You say you had to replace the MAP sensor. Did you double check that the sensor itself is not defective, the vac. hose undamaged, and that the double-titted grommet at the throttle body was installed right way around?
 
Matthew Currie said:
How about the throttle body to the manifold? Make sure no leak, bad gasket, etc. there.

Can we assume that you have eliminated any and all mechanical issues with throttle linkage? I say that because my 87, which had a taste for variety, managed to provide high idle problems not only from a rusting accelerator pedal pivot, but later from a worn and binding bushing on the throttle linkage bell crank, in addition to the usual sticking IAC pintle and a just plain worn out throttle body. Every time I would replace one thing, another would pop up.

You say you had to replace the MAP sensor. Did you double check that the sensor itself is not defective, the vac. hose undamaged, and that the double-titted grommet at the throttle body was installed right way around?
Click to expand...

All good questions, reminds me that my last 3 or 4 high idle incidents were the damn floor mat, slipped up under the gas peddle, :eek: LOL!!!
 
ya mine is under the hood with that bottle and like i said we checked every where possible for leaks so could be a bad IAC still or like u both said throttle pedal or something like that. ill check these few things and hope its something stupid lol
 
QUOTE from Matthew Currie in post #11
“You say you had to replace the MAP sensor. Did you double check that the sensor itself is not defective, the vac. hose undamaged, and that the double-titted grommet at the throttle body was installed the right way around?”
----------
Note from DJ
On my 88XJ there is a rubber grommet that plugs into the throttle body. You have to be careful because there are two holes in the throttle body and you can actually put the grommet in upside down if you are not careful. The MAP hose plugs into the part of the grommet that has a hole in it, that portion of the grommet goes in the lower hole. The top hole is plugged by the blank tited portion of the same rubber grommet.

You might want to take a look to make sure that when you installed the new MAP sensor you didn’t goof up the grommet part of the installation.

I would most defiantly check to make sure the new MAP test out according to specks. There has been a rash of replacement parts that were defective out of the box lately.

What made you think the original MAP was defective in the first place?
May be someone might see a clue to your ongoing problem in your original symptom’s.
 
cause the shop said it was bad cause it would not run at all. it would fire up then die and soon as we replaced it it ran fine for 4 months then starter doing the high idle and stuff
 
ok so i messed with it today and i checked the TPS with my meter and nothing. tried every setting on it and didnt do anything and i fired it up after 10 min of cranking it. it started and went to 1200 then dropped to 750 to 800 and idled. after a few mins it jumped to 1500 or so then back to 750 then back to 1200 then died. is it a bad TPS or Idle air control valve ?
 
jamesxjowner said:
ok so i messed with it today and i checked the TPS with my meter and nothing. tried every setting on it and didnt do anything and i fired it up after 10 min of cranking it. it started and went to 1200 then dropped to 750 to 800 and idled. after a few mins it jumped to 1500 or so then back to 750 then back to 1200 then died. is it a bad TPS or Idle air control valve ?
Click to expand...

THE IAC is good if it is changing the idle speed up and down. It only does what the ECU tells it to do. Something is giving the ECU bad data, like a bad TPS or bad TPS wiring in the harness.

What exactly does "i checked the TPS with my meter and nothing" this mean?

"Nothing" is useless info, we need DATA!!!! The meter (?) did nothing, or the TPS did nothing? Or some other "it" did nothing, LOL!

You tried every setting on what?

Reread my old post!!!

First off, reminder that this is 90, not a 92 jeep, so a bad ECU is not all likely. There is no MAF sensor on XJs.

EGR problem is possible!!!! Including a bad EGR diaphragm leaking vacuum!!! bad air manifold or coolant temp sensor is possible.

Most likely is a growing (but not yet located) vacuum leak while it warms up.

Vacuum can leak at the brake booster, the bottle in the bumper!!!!!, the hoses under the battery, leading to the bumper bottle, the AC vacuum lines, inside the cab and under the hood, the EGR, the egr solenoid, the MAP sensor to throttle body vacuum line and along the rear firewall, and at the throttle body and the I-manifold.

A bad Intake temp sensor will cause high idles too!!!! Ask me how I know!!:doh:

You say the grounds are good, but what data results did you get, how did you verify the grounds?

One other though is a an FPR diaphragm leak of gas into the vacuum lines, or leaking injectors, adding fuel, but that usually causes other issues too, like a flooded engine hard start.
Click to expand...
 
FWIW, a bad IAC, as in dead, would cause a fixed idle once warmed up,

or an idle that went up or down as the engine warmed,

but not a wandering, up-down-up-down idle. Dirt clogging the IAC port in the throttle body could cause the idle to change at random, but that is fixed by cleaning the throttle body port where the IAC seats.

Yours sounds like a wiring or TPS (maybe), but you did NOT supply any test data???? So there is no way to answer your question.
 
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