A little confused/frustrated
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Member
Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
I'm parking this @#$%^& until Saturday and will work on it then. At this point, I've had little sleep and exhausted myself with frustration. I have to work soon, so !@#$# this thing for now. Thanks for all the input.
CF Veteran
Joined: Aug 2010
Posts: 2,112
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From: Wantage, NJ
Year: 1995
Model: Cherokee
Engine: 4.0 I6
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From: Elizabethtown, pa
Year: 1994
Model: Cherokee
Engine: 5.2
Not being a d bag man. Just trying to help you out. It has to be something vaccume related, MAYBE pcm, but doubt it. What does it do with the IAC unplugged?
Thread Starter
Member
Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
No the vac line goes up to a bracket at the top of the firewall behind the TB. That sensor is the MAP.
Check all the vac fittings and every part of the line
Injectors is a possibility, Id go ahead and check them along with the Fuel pressure regulator, alternator and reset the PCM. If the fuel pressure is to low the ECU would raise the idle speed to accomodate. If the alternator is going bad the computer could attempt to make it idle higher to achieve the correct power output.
Check all the vac fittings and every part of the line
Injectors is a possibility, Id go ahead and check them along with the Fuel pressure regulator, alternator and reset the PCM. If the fuel pressure is to low the ECU would raise the idle speed to accomodate. If the alternator is going bad the computer could attempt to make it idle higher to achieve the correct power output.
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Member
Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
Shes cooked.......
The PCM is cooked. Found one out of an insurance totaled heep for $215 with a one year warranty. Is this a plug and play deal or does it need to be dealer flashed? Sold some tires to a certified mech today (who also owns an XJ that is insane) and he said that the dealer flashing is BS. I've gotten all sorts of answers, but he is credible. Figured I'd see what the folks here would say.
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Joined: Jan 2010
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From: MI
Year: 2000
Model: Cherokee
Engine: 4.0 I6
Just out of curiousity, how did you determine that the PCM is fried? This is kind of like a math problem with just an answer and no variables to show the work.
I'm curious because I wouldn't even know how to test a PCM, let alone know if it is bad. 
I'm curious because I wouldn't even know how to test a PCM, let alone know if it is bad.
Thread Starter
Member
Joined: Mar 2009
Posts: 222
Likes: 1
Year: 1999
Model: Cherokee
Engine: I6 4.0L
Diagnostic scanner....one I can't afford. I'm actually going to go with these guys on ebay (ACE) and get one of theirs for 165 bucks. Guaranteed plug and play. You send them your vin, mileage, etc.. The units are fully rebuilt and tested.
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From: MI
Year: 2000
Model: Cherokee
Engine: 4.0 I6
Cool. Thanks for the explanation. Yeah, diagnostic scanners are way out of my league too...But, what would a 'backyard mechanic' have to do with a $7k scanner? LOL
Thread Starter
Member
Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
Thread Starter
Member
Joined: Mar 2009
Posts: 222
Likes: 1
Year: 1999
Model: Cherokee
Engine: I6 4.0L
Senior Member
Joined: Jan 2010
Posts: 712
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From: MI
Year: 2000
Model: Cherokee
Engine: 4.0 I6
Thread Starter
Member
Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
Troubleshooting can get frustrating, especially when it comes to electronics. I had a 97 TL1000 that had a bunch of sensors and relays. I'll let you guys know how it works out.
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Joined: Mar 2009
Posts: 222
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Year: 1999
Model: Cherokee
Engine: I6 4.0L
Sorry it took so long to reply. I got the ECM from ebay, installed it and......still had problems., The high idle was gone but it shifted early and had a 3000rpm stutter. I ended up having a defective TPS. Put the old one in and bing it runs fine. Returning the defective sensor offset the price of the scanner. The scanner was the best money I spent for the Jeep. I HIGHLY RECOMMEND IT. IT WILL SAVE YOU TIME AND MONEY!It was 55 bucks. Thank You all for all of your help!