1989 Cherokee 4.0 Barely runs - JeepForum.com
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Unread 03-24-2013, 09:10 PM   #1
Trooka
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1989 XJ Cherokee 
 
Join Date: Mar 2013
Location: Mt. Vernon, WA
Posts: 2
1989 Cherokee 4.0 Barely runs

Ok, so I have searched the forums for days now. I have found similar problems but not exact as mine. my problem is my Jeep is barely running, it pops, backfires, spits, sputters, backfires through intake, well yeah thats about it. I purchased it 4 days ago, so far I have tried 2 different ignition control modules, cleaned intake, cleaned throttle pos sensor, cleaned IAC, replaced spark plugs, all have had absolutely no positive changes in the idle, or rev. I know the timing is non adjustable, but I didnt know that before and attempted to twist the distributor to adjust the timing. call me crazy but it did change it. it made is so the thing would idle but still any throttle at all it would fall flat on its face, and pop backfire and sputter. since then if I start it again it will not idle correctly again. tomorrow I am going to check fuel pressure, I also checked the resistance of the Crank Position Sensor it was within operating range. also the previous owner said it happened 1 month after the local mechanic shop replaced the clutch. when you try to start it now I believe they screwed something up in the clutch because it will make some nasty metal on metal noises out of the tranny/flywheel/starter. any help would be much appreciated!

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Unread 03-24-2013, 10:50 PM   #2
bigbadduck
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1987 XJ Cherokee 
 
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Posts: 83
Sounds like your fuel pressure is too, check pressure at rail you should have 39 psi at idle. If pressure is low check fuel filter and pump.
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Unread 03-25-2013, 06:16 AM   #3
sbaird95
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2000 TJ Wrangler 
 
Join Date: Nov 2010
Location: Huber Heights, Ohio
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Quote:
Originally Posted by bigbadduck View Post
Sounds like your fuel pressure is too, check pressure at rail you should have 39 psi at idle. If pressure is low check fuel filter and pump.
x2... also check the strainer in the fuel pump, sounds like the problems i had when my strainer was clogged.
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Unread 03-25-2013, 07:28 AM   #4
ComancheKid45
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1988 MJ Comanche 
 
Join Date: Sep 2008
Location: Shippensburg, PA
Posts: 494
Check your map sensor and the vaccum line associated with it.
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Unread 03-25-2013, 06:25 PM   #5
tjwalker
It's the crank sensor!
 
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1999 XJ Cherokee 
 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,408
Actually the fuel pressure spec for an 89 is 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should then jump to approximately 39 psi.

Be sure that the vacuum line is pulling good vacuum line and is not wet with fuel. If it is wet with fuel, you have a ruptured fuel pressure regulator.

If all that checks out, I agree with testing your MAP sensor.
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Unread 04-04-2013, 07:49 PM   #6
Trooka
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1989 XJ Cherokee 
 
Join Date: Mar 2013
Location: Mt. Vernon, WA
Posts: 2
diagnosed...

so you guys are probly gonna poop chickens on this one. after EVERTHING checked out I decided to drop the tranny and possibly part it out. whomever replaced the clutch forgot to tighten and/or threadlock the flywheel bolts. at low RPM's the flywheen was off balance giving the crank pos sensor enough of a reading to run but not much else. so tighten and lock the bolts, put back together and tadah... 400$ jeep fixed. thanks a bunch for your help everyone. and im sure I will be needing your help again. hopefully not but lets be real.... its a jeep after all....
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Unread 04-24-2013, 10:30 PM   #7
Simmbad
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1989 XJ Cherokee 
 
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Location: Modesto, Ca
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nice glad you fixed it
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