1990 Cherokee 4.0 losing power - JeepForum.com
 
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post #1 of 10 Old 11-29-2013, 03:40 AM Thread Starter
deepsnow4days
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1985 XJ Cherokee 
 
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Location: Windermere
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1990 Cherokee 4.0 losing power

Hey there
This is my first post really hoping i can find a few answers here.

My problem I have I noticed about a month ago when I was driving up to northern alberta for work. Starting the rig cold I would head out on the highway and it would be running fine exactly how I'm used to it running. The further I go the more I notice it to start losing power (High-ish RPM) It would get to the point where on a hill it would start to lose power sputter/spit/and hesitate where I would have to gear down into 3rd (sometimes 2nd!) just to keep some sort of a speed up on the highway. I had a problem recently that was sort of the same as this the only difference was that it was sputtering spitting and hesitating at low RPM's when i was trying to get going then once i got to a certain RPM range it would stop. I ofund the root to that problem was that my main manifold vac line had completely snapped ontop of the tranny cuasing the low RPM sputtering...... so... thinking that vac was still my issue i gutted out the entire vac system and inspected the lines for leaks using several techniques as well as hooking it and running a vac gauge off each line which i found no problems or leaks with and my dad ( the family mechanic) pointed me in the right direction that vac leaks cuase low rpm issues and that vaccuum was not my issue in this case...... so jumping the gun a little i replaced the fuel filter, dried out my dist. cap, replaced spark plugs.......same sypmtoms occurred... so i got as basic as i could and started thinking electrical becuase one morning i noticed it was a little harder to start as if the battery/starter/altenator was lagging on me......i took my voltmeter and realized that all the cables running from my battery were rotting out and worn out from constant on and off throughout my project......i replaced all the wires leaving the battery and now it starts good and strong.....just today expecting that the battery wires fixed the problem i drove it to work ....was running fine until about 20 km's went by and it started doing it again whenever i needed power on hills i would press the gas further down and it would spit sputter hesitate and cause me to gear down however not quite as bad as before i replaced the cables .... I could use anyhelp i can get...

also any pointers on this whole forrum thing can help as well really trying to get involved with jeep communities....Ive been slowly building up and learning about my cherokee since i got it about 5 years ago.


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post #2 of 10 Old 11-29-2013, 05:57 AM
cruiser54
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Could be a coupla things. Spitting and sputtering leads me to your dizzy cap, rotor and plug wires. Often overlooked in a tune-up. At the daler, we replaced all that every 30K miles. The wires were the weak link.

Click on the link below and go to post #1. It might help since you mention an improvement after replacing the cables. It should be done regardless since it addresses a well known weak link.

If you own a Renix Jeep, you'll want to check this out.

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post #3 of 10 Old 11-29-2013, 10:57 PM
compfreak530
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Well sounds to me like your Catalytic converter may be getting clogged up. or your fuel pump is no longer able to keep up with the fuel demand of the engine during high demand. couple of ways to test this is get a vacuum/pressure gauge T in to a main vacuum line and watch it. depending on your altitude it should be between 15-23 ish.. while crusing <you will need a long peice of vacuum hose. watch the gauge. as the exhaust heats up the converters clog and restrict flow causing it to run poor. another possibility is as your fuel pump heats up it starts producing less output.. less fuel less power. only real wya to check is with a fuel pressure gauge.. but to me it sounds like your exhaust is getting restricted.
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post #4 of 10 Old 11-30-2013, 04:14 AM
cruiser54
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Here's an exhaust test that you can do without driving:

CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION

Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below

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My Jeep Technical Photos

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post #5 of 10 Old 11-30-2013, 04:45 AM Thread Starter
deepsnow4days
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Hey thanks guys I'll give those tests a try and let yeah know what happens

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post #6 of 10 Old 12-01-2013, 07:48 PM
zman6988
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I agree with compfreak530 sounds to me like your Catalytic converter is going on you. Don't know what your emission laws are were you live but if they are like mine in NC then gut it out and drive it to see if that fixes the issue.
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post #7 of 10 Old 12-01-2013, 08:07 PM Thread Starter
deepsnow4days
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Hey guys so the old man and I did some trouble shooting .... I was thinking fuel pump just cuz usually with my luck the worst thing that can happen will happen however I wanted to make sure it wasn't electrical before I went about the process of pullin a pump and making myself smell like fuel all day....we disconected every plug in the eng compartment re crimped connections and scrubbed out all the plugs with CLR a few connections were a little loose and sketchy likely from my pre existing death wobble that I recently corrected .... Dried out the connections with a heat gun and slapped it all back together.. Took it for a drive ran awesome ..... I have driven about 150 KMs in total today and the problem appears to be resolved ... Running even better then before.. Thanks for the input guys

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post #8 of 10 Old 12-01-2013, 08:10 PM
cruiser54
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Glad to hear it. Excellent job.

R*C*B*R*C= Refresh Connections Before Replacing Components

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below

www.cruiser54.com

My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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post #9 of 10 Old 12-01-2013, 08:12 PM Thread Starter
deepsnow4days
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Location: Windermere
Posts: 9
P.S. For anyone who is possibly ever having the same issue ... The connection that was the worst was a sensor on top of the intake manifold .... I don't have my manual with me so I wasn't able to look up what it was .... However that is what the likely culprit was.

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post #10 of 10 Old 02-28-2014, 01:02 PM
ChipsXJ
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Pic of the sensor?

1993 Jeep Cherokee
4.0 Auto 4dr 4X4

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