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I have a 1993 Jeep Cherokee that blew a motor at 270,000 when the water pump failed. I put a used motor from a wrecked 1992 Jeep Cherokee that had 98,000 miles on it. It now blows black smoke and misses only at an idle and not when you are driving down the road. Does anyone have any thoughts as to what the problem is?
 

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It sounds like there may be an issue with the computer "talking" to the new motor. They seem close enough to not matter, but you may need to swap in the old O2 sensor or any other electronic components that were attached to the old motor.
 

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It sounds like there may be an issue with the computer "talking" to the new motor. They seem close enough to not matter, but you may need to swap in the old O2 sensor or any other electronic components that were attached to the old motor.
What you should do is bring the computer off of the donor vehicle and transplant that aswell since that computer was specifically built for that motor.
You are both jumping on the computer bandwagon without thinking this through. You sound like a dealership mechanic.
The injectors are plug in wiring and at least one may have a bad plug or is not plugged in well. The computers are the same one for both years.
After the revs get high enough the impulse will make the jump on the injector. Or one injector got dirt in it that affects it's operation at idle but the increased pressure at higher revs will allow enough fuel to run better.
 

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You are both jumping on the computer bandwagon without thinking this through. You sound like a dealership mechanic.
The injectors are plug in wiring and at least one may have a bad plug or is not plugged in well. The computers are the same one for both years.
After the revs get high enough the impulse will make the jump on the injector. Or one injector got dirt in it that affects it's operation at idle but the increased pressure at higher revs will allow enough fuel to run better.
I'm going to second a fuel delivery issue... Too much unburnt fuel = black smoke.
 

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I think I might have stumbled across the most fun web site. I came across this web site by accident when trying to figure out what was wrong with my jeep, being as I am a girl and not a mech at all, I am finding alot of really good ideas for my cherokee. Thank you all, I will be visiting often!
 

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I think I might have stumbled across the most fun web site. I came across this web site by accident when trying to figure out what was wrong with my jeep, being as I am a girl and not a mech at all, I am finding alot of really good ideas for my cherokee. Thank you all, I will be visiting often!
Very glad to hear it:rock:
 

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Looks Like I'm on-but my Pic of Jeep upload was rejected.Maybe file too big????
Anyway-mine's in Panama, Central america-exported from Miami last dec.
I need advice on stumbling uphill/against wind after driving for 30-40 minutes.[/B]
When it's cold it runs ok for a while at first-lots of power.
Idles-revs ok in park-perfect.
It has 113 miles-new motor at about 100.Previous owner overheated it and drove 1st motor to engine heaven.
Engine always stays at ok operating temp-200-210-never more.
No "missing"-like when it's a bad single plug-or wire.
If I keep on-then-off gas-on and off-on and off-it will keep going -even when stumbling.
Has never totally quit.
After much,much research online about these symtems- I have come to some conclusions about what the probable problem is-but- I want to hear from the CT group of experienced owners-to confirm my specific suspicions.
allan
ps- I want to continue my adventure in Panama with my Cherokee for a few years.
 

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It sounds to me like it could be a fuel problem. I'm not completely sure but if its only uphill that this is happening when a higher fuel demand would be needed, if its not getting a full supply of fuel it would "stumble" as you say. I'm not saying this is the problem though because I'm not completely certain, but it could need a new fuel pump, injectors, etc.
 

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X2... I agree with the fuel problem, but also I'd take a look to see if you have any leaks, drips, or weeping out of any connection in the fuel system. It's free and somewhat simple, and being that it is a closed system, any air that could get into the system could cause a fuel problem, whether it's sucking a bit of air or it's not pumping to capacity.
I'd also recommend a fuel pressure test, check the pres. reg., and change the filter.
 
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