Patience dear, patience. Cherokee still hates me...

[CaptainZoom]

Dear all,
I´m about to go completely bezerk over my -89 Cherokee.
Been here "many o´times" with this problem before, but without sucess so far. -So I´ll give it another go. Here here are the symptoms:

¤ Always starts up fine. No problemos
¤ Runs OK, when cold (Not Great, but OK")
¤ Low idle, about 600-850rpm. And a bit jumpy and jerky. Up and down, up and down...
¤ As soon as engine starts to get a bit hotter, let´s say after ca 1-1½min, It starts to run a bit worse, but not terrible.
¤ Engine keeps stalling for no apparant reason!!! Quite often actually. But always starts up without hesitation again. Just turn the key.

¤ Found that it normally happens when easing or letting go of the gaspedal. As long as I keep accelerating it runs fairly fine, but as soon as I let go of the gaspedal or ease on it, It dies just like somone turned off the ignition key. But its only the engine that dies, all the other electric system is fine and keeps on working. So while still rolling I just put gear in "N" and start her up again. -And it seldom happens whith cold engine.

These are the things I´ve checked, replaced, or in other way ruled out. A friend has one of same year and model, so I have tried components from his car at some points to rule out defective ones on mine.

Cleaned out throttlebody
TPS
Flywheel sensor (CPS?)
EGR valve
Fuelfilter
Ignition module/coil
Sparkplugs+cables
Rotor+cap
Fuel resistor? (white ceramic, found in inside fender, drivers side)
New "Red Top" battery
New intake manifold
Visually checked vacuum hoses

Since the problem seldom happens when engine is cold and seems to be related to when engine starts to get warm or has reached normal working temp, I´m thinking some kind of sensor telling the computer to switch from "cold engine" to "normal working mode" or such. Perhaps some temperature related sensor?
I´ve been told by a Chrysler mechanic that not all sensors are in operation until engine has reached working temp? Anyone know?
I found a link here before, to a site where one can find specs on all sensors in the 4.0L engine, and also how to check them with the voltmeter. But I can´t find it again.

If there´s anyone whith an idea, tip or trick to faulty diagnosis?
I´d be so grateful!

[CaptainZoom]

By the way. Forgot to mention, (and I don´t know if it matters, but maybe?)
I can feel the engine revv in the brakepedal?
If I keep the brakepedal depressed, and revv the engine up and down, I feel the resistance in the brakepedal becoming softer. As if the power brakesystem is working.
Since so much on these cars are controlled by vacuum,including ignition, could this be some kind of help to pinpoint the problem?

[jwalden]

Just an idea, you may have a vaccum leak. With the engine running try spraying carb. cleaner around your intake, throttle body and anything else that has vaccum. If your rpm's change, then you found a leak.

[altenburgpj]

My 93 ran great at all times, then suddenly die often at 30 to 50 miles per hour. This often happened when the heat was on high temp and low speed fan in the winter. I thought it was a control box under the dash on the passenger side getting hot.

Tired of running the heat on medium, I disconnected the battery and took apart every multipin connector to every control box (even the ECU under the hood). Cleaned the pins with a pencil eraser, contact cleaner, compressed air to dry, added grease and put it all back together.

Success, 18 months, 10K miles no problems.

[CaptainZoom]

Brothers in Jeep´s!

"jwalden"
Thanks man. -A good idea, but...
When all this started, I took the car to a Chrysler mechanic, who hooked the car up to a computer. The reading said "Vacuum loss"
The spray was the first thing I tried to localize eventual vacuum loss. (Actually I used "Motor-starter", but it works the same way)
And that´s how I came to find the leak in the intake manifold gasket. -Which I then replaced.
The car ran a bit better after this, but still not nearly good.

"altenburgpj"
I have checked a lot of the cables and connections, but it´s possible I missed some...

Anyway, thank´s a lot for all the input folks!
If You come to think of anything else, please let me know. All ideas are welcomed, no thought is stupid or funny in this case. It´s probably something obvious I overlooked or missed..

[altenburgpj]

I knew a guy once who owned a LTD, and the dealer tried to trace a dead engine problem, after towing it to the dealer 3 times, and replace the ECU twice, his local mechanic tightened a screw on the ground cable under the dash that grounded the ECU. You never know.

Originally Posted by CaptainZoom

If You come to think of anything else, please let me know. All ideas are welcomed, no thought is stupid or funny in this case. It´s probably something obvious I overlooked or missed..

[badron]

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Low idle, about 600-850rpm. And a bit jumpy and jerky. Up and down, up and down...
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This STINKS of vacuum leak. or bad EGR value

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¤ Runs OK, when cold (Not Great, but OK")
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Warm-up mode: She blow off O2s in this mode and runs real rich can cover up a leak again bad intake value(s) bad EGR and/or EGR controllers

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As long as I keep accelerating it runs fairly fine, but as soon as I let go of the gaspedal or ease on it, It dies just
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She might be in the power mode: one again blowing off the O2s and running rich covering up a small vacuum leak, bad EGR/controller and bad intake value(s), bad head, bad intake to head gasket, lose carb or what ever you got bolts, bad brake booster, ETC.ETC.

Sorry if this is all old news but I bet a steak diner and free beers that you are sucking air somewere.Luck

R Robinson

[jwalden]

Maybe try the pick up coil inside of the dist. Sometimes they can act weird and gives a weak signal.

[CaptainZoom]

True,
Loose groundcables can be a pain, and usually causes the car to behave in the most strange ways.
Had a Volvo 740GL once that was a bastard to start in the morning, or if it just had rained...
Once started, it ran 100% and no problemos to start it later the same day. It was just that first start of the day.
Turned out to be an oxidated cable connection. But before I found it...

A friend checked the EGR,(the only thing I didn´t do myself) and I think it´s OK. Im not so sure how to control the EGR valve, but if anyone knows how to check it..?
Looks like I have missed something when looking over screws & bolts, hoses & lines.
I will check up on all these tips and see where they lead me. Thank´s a zillion for all input.
-And again, If You come to think of something else...

[altenburgpj]

Here are the basics of how and EGR works.

www.fordscorpio.co.uk/egr.htm

[Saudade]

Here's one with some troubleshooting for the Jeep.

http://www1.autozone.com/servlet/UiB...3d801525ce.jsp

[CaptainZoom]

Ahaaa! so that´s what the little fella´ does, eh?
I´ll have some serious palaver with Mr.EGR and tell U guys what I´ve found out.
Thank´s again!
Carl

[Saudade]

Good Luck Carl, Let us know how it goes.