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View Full Version : Need Cherokee troubleshooting help


maxsdad
08-13-2010, 10:09 AM
I know, I know...it's a J**p....
But it's my daughters, and she got it free, and it's all she can afford.
It's an 89 cherokee laredo with the 4.0 liter renix based injection sytem. It all of a sudden started running really rough and we had it towed home about a month ago. Since then, we've been trying to figure it out...new cat, new tps, new cps, new o2 sensor, new bunch of other sensors...cleaned out throttle body and injectors, new plugs, new bunch of other stuff....we thought maybe it was bad gas, so we drained the tank and replaced with new gas...let it run for about an hour...still no luck...
This pos has no check engine light..there is a proprietary tool that can read codes but hardly anyone has one anymore....some dealers have them, but I don't want to pay more for a diagnosis than the car is worth.
Anyway...I was hoping there might be a Cherokee pro out there who could help us diagnose the problem.
Can't afford much in the way of payment, but can certainly provide :beer::beer::beer: and food!!
Thanks in advance for any help.

RedCreeper
08-13-2010, 10:30 AM
Fuel Filter? Vacum? Check all your wires and lines. That old something may have come loose or kinked. I have a buddy that knows them better i will ask and see if he has any ideas.

maxsdad
08-13-2010, 10:42 AM
Thanks!
New fuel filter and pump...checked the vacuum lines a million times in the last month...can't see any wires disconnected or melted. No fuses blown, we also changed the map sensor...unhooked the battery after changing out the sensors, gave it time to reset. Compression is OK, as is fuel pressure. EGR valve seems to be working ok.Fuel Filter? Vacum? Check all your wires and lines. That old something may have come loose or kinked. I have a buddy that knows them better i will ask and see if he has any ideas.

RedCreeper
08-13-2010, 10:50 AM
OK left him a message. I will see what he has to say. Can't remember but isnt there two fuel filters?

maxsdad
08-13-2010, 11:04 AM
Hmmm - That I'm not sure about...I'll check.
And thanks for your help!OK left him a message. I will see what he has to say. Can't remember but isnt there two fuel filters?

Chris
08-13-2010, 02:16 PM
Hey Rob, I'm not sure what the problem is (starting? running? etc) but this may be the solution you're looking for or maybe give you some leads to check.

Starting Problem Solved (http://www.frontrange4x4.com/forums/showthread.php?3293-XJ-starting-problem-solved)

maxsdad
08-13-2010, 02:36 PM
Thanks Chris - I'll look at it closer this afternoon. Just got back from a little more troubleshooting and this is what I found this round - I unplugged the map sensor and I could not get the car to start. I plugged it back in and unplugged the map sensor vacuum line and the car ran 100% better with the vacuum line just sitting there - the minute I plugged the line (I could feel vacuum) the engine started to die???
Hey Rob, I'm not sure what the problem is (starting? running? etc) but this may be the solution you're looking for or maybe give you some leads to check.

Starting Problem Solved (http://www.frontrange4x4.com/forums/showthread.php?3293-XJ-starting-problem-solved)

Chris
08-13-2010, 02:54 PM
Beats me Rob but I know some people that may be able to help. I can pass on some phone numbers if you'd like to toss it around with someone else.

maxsdad
08-13-2010, 02:55 PM
Hey Chris - Thanks - that would be great - it's apparently a commonish problem with the 87-90 Renix 4.0 litre engines - RobBeats me Rob but I know some people that may be able to help. I can pass on some phone numbers if you'd like to toss it around with someone else.

rover67
08-13-2010, 02:58 PM
Weird...

Can you test the MAP sensor to make sure the thing is putting out the right range of voltages for the vacuum it is seeing?

We have a 2000 Cherokee with what is probably a similar setup (maybe not) and it intermittently runs REALLY rough. Usually it clears up within a few minutes or after shutting it off. no help i know.

I'll pull the vacuum line off of mine (drove it to work today) and see what happens just for comparison's sake.

Chris
08-13-2010, 03:22 PM
PM'd you a couple guys Rob.

RedCreeper
08-13-2010, 04:39 PM
sounds like something is up with the mapp sensor. Have you replaced it?

maxsdad
08-13-2010, 04:56 PM
Thanks Chris!PM'd you a couple guys Rob.

Yep - replaced with same result...sounds like something is up with the mapp sensor. Have you replaced it?

RedCreeper
08-16-2010, 12:26 PM
Sorry for the time it took to get back with you. My buddy suggested cap, rotor and timing chain. this was before he knew about the mapp sensor. He also mentioned there might be a sensor in the ditribitor that might be acting up. When i told him about the mapp sensor issue he said to check the vacum lines for blockage or leaks.

maxsdad
08-18-2010, 03:06 PM
My turn to say sorry...been ultra busy...
The sensor in the distributor is the cam position sensor. We did look at it and clean it up a bit, but have not tried to replace it..I think there's a multi meter test you can use to determine whether it's working correctly or not - we'll look into it.
Checked all the vacuum lines - they are fine.
Thanks to your friend for his advice.
Sorry for the time it took to get back with you. My buddy suggested cap, rotor and timing chain. this was before he knew about the mapp sensor. He also mentioned there might be a sensor in the ditribitor that might be acting up. When i told him about the mapp sensor issue he said to check the vacum lines for blockage or leaks.

rover67
08-18-2010, 03:08 PM
I finally looked at the Jeep I am driving today... and it looks like it is a different setup. the MAP sensor is bolted to the manifold...

Sorry bout that.

RedCreeper
08-18-2010, 03:17 PM
NP. Hope you get it figured out. I know on my old Jeep it was vacum lines that always cause my issues. But it was carberated also. Once i had a loose main power wire to the computer. Kept shutting off or ran like crap and could not figure it out. A month later of cussing and fussing and tow bills we found it. Hope yours does not take that long or is as much trouble. Let me know what you find out and if it stills needs a few ideas to figure out i can run it by him. Sorry if it is slow to get back he is in the middle of a house hold blending pot at this time. New lady and 3 new kids to go with his two.... DOH!