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Unread 02-22-2011, 02:28 PM   #1
JenLees
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1986 XJ Cherokee 
 
Join Date: Feb 2011
Location: Tacoma, WA
Posts: 8
Car stalls and won't start when engine hot

Help! I have a 1986 Jeep Cherokee Pioneer 4 cyl 2.5l 5 speed manual. I can start the engine and drive for a while, then when the engine warms up, it stalls and won't start up until the car cools down for at least 30 minutes.

This problem started with the car not starting if I stopped the car after driving a short distance (like when I got gas then couldn't get it started again). It cranks but won't catch. Now it will stall while I'm driving. Three times I've slowed down or come to a stop and when I hit the gas, nothing. It sputters and backfires from the engine like it's not getting enough or any gas. Both times I was able to get it into a parking lot and let it cool down.

I've replaced the spark plugs, wires, distributor cap, rotor, MAP sensor, and TPS.

The fuel pump comes on, but I think it may be staying on as I drive (sounds kind of like a jet engine).

I have purchased a new CPS, a fuel pump and filter but haven't attempted to replace these yet. I replaced the easy to get to stuff first.

So...does anyone have a guess as to what it wrong? I've been reading that the CPS can cause a bunch of problems but it looks like getting to it is a challenge. But so does the fuel pump.

Any suggestions are appreciated! I love this Jeep and want it to run well

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Unread 02-22-2011, 02:53 PM   #2
440_Magnum
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1999 XJ Cherokee 
 
Join Date: Jun 2008
Location: Austin Texas
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The usual suspects for stalling when hot: fuel pressure, vapor lock, weak ignition components (especially the coil and control module).
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Unread 02-22-2011, 04:19 PM   #3
tjwalker
It's the crank sensor!
 
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1999 XJ Cherokee 
 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,406
Suspects: In this order..........

#1. Crankshaft position sensor
#2. Ignition coil
#3. Ignition control module (under the coil)
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Unread 02-22-2011, 04:22 PM   #4
troys96xj
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1996 XJ Cherokee 
 
Join Date: Nov 2009
Location: Ravenna , OHio
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My 4.0 did the same thing. I pulled the manifold air temp sensor and cleaned it really well with carb cleaner and it's been good for over a year now.
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Unread 02-22-2011, 05:00 PM   #5
exsane
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1996 XJ Cherokee 
 
Join Date: Feb 2011
Location: chambersburg, pa
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sounds like the crank sensor. happened to mine all time. i would be riding, and it would get hot and jeep just shut off, and i would have to let it cool down tos tart it back up. replace your crank sensor and i bet you will be fine. just it's a lil pain to get to it.
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Unread 02-22-2011, 05:21 PM   #6
MCrock
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2001 XJ Cherokee 
 
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I agree with the Crankshaft position sensor. My 97 BMW used to do this. Replaced a lot, including CPS and thats what seems to take care of it. Good luck!
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Unread 02-22-2011, 05:33 PM   #7
troys96xj
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Check the M.A.T sensor before you put the CPS on. If it's the mat sensor and you put the CPS in then you can't return it. Also, if it's the mat then it's a free fix.
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Unread 02-23-2011, 09:34 AM   #8
JenLees
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I will definitely try the MAT sensor but with all the info on the CPS I've found I bet that's it. I'll be working on it this weekend, if it doesn't snow.
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Unread 03-08-2011, 10:45 AM   #9
JenLees
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Well I tried cleaning the MAT sensor but it didn't help. Drove it 30 miles today no problem but when I got to my destination I tried to start it up again and it wouldn't start. It sputters and backfires. When it cooled off completely I was able to start it up again. Guess I'll try replacing the CPS this weekend. Been avoiding getting under the car. Any other suggestions? Thanks
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Unread 03-08-2011, 07:09 PM   #10
JenLees
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Another update...

I drove it home on the freeway, 30 miles. Got off the freeway and it started to sputter, buck, and backfire in the throttle. I got through the intersection and it accelerated fine for a few blocks. I turned onto a less busy street and when I got to a stop sign, when I hit the gas it sputtered, bucked, and backfired again and wouldn't accelerate. I got it around the corner into a parking lot, and again it seemed fine. I went around the block,, got across the street, and got it home. Turned off the car, started it again and it started right up.

My observations while driving on the freeway are that it was accelerating but seemed to hesitate a lot, especially on inclines. Not a lot of power in general but was able to get up to 65mph(it's a 4 cyl so I don't expect too much). Fuel pump sounds like it's constantly running.
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Unread 03-08-2011, 10:09 PM   #11
Flyordie
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1985 XJ Cherokee 
 
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Ignitor Box? $20. 2 Plugs and you are good to go.

Had the SAME exact problems. Ignitor box was going and it would start but idle like crap (if warm). Any throttle and it would just drop dead. However, before you get it, borrow an induction timing light and try to replicate the problem with that light on. Just point the light anywhere and look for breaks in the light.
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Unread 03-25-2011, 09:02 AM   #12
JenLees
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1986 XJ Cherokee 
 
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Location: Tacoma, WA
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Ended up taking it to a mechanic. The stalling problem was one (or all) of three issues. Bad fuel filter, CPS wire melted onto exhaust, and (I NEVER would have figured this out so glad I took it to a mechanic) someone had messed with the fuel injector wires and spliced them incorrectly. Fixed everything and it's running wonderfully.

Now on to fixing two front seats that won't flip forward.
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