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Discussion Starter · #1 ·
1989 Wrangler 4.2L with complete top end from a 94 cherokee (MPI system & harness, sensors, etc)

Okay so I drove 250 miles through the AZ mountains no problem but as soon as I hit I-40 I got about 30 or so miles in and the engine suddenly started missing real bad then just cut out completely

I tried restarting it but it would just sputter and die instantly, or just crank with nothing

I let it sit there for about 20 or 30 minutes and it started up fine like nothing was wrong


it did this about 9 or 10 times so far, I made it to Albuquerque at least

I replaced the coil pack the first time it happened because I thought that was it, but it did it again about 30 miles later so I thought it was the TPS and unplugged that sensor, drove fine for another few miles then started doing it again, so I tried the MAP sensor, same thing

there are no check engine codes coming up, that is what frustrates me
 

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1989 Wrangler 4.2L with complete top end from a 94 cherokee (MPI system & harness, sensors, etc)

Okay so I drove 250 miles through the AZ mountains no problem but as soon as I hit I-40 I got about 30 or so miles in and the engine suddenly started missing real bad then just cut out completely

I tried restarting it but it would just sputter and die instantly, or just crank with nothing

I let it sit there for about 20 or 30 minutes and it started up fine like nothing was wrong

it did this about 9 or 10 times so far, I made it to Albuquerque at least

I replaced the coil pack the first time it happened because I thought that was it, but it did it again about 30 miles later so I thought it was the TPS and unplugged that sensor, drove fine for another few miles then started doing it again, so I tried the MAP sensor, same thing

there are no check engine codes coming up, that is what frustrates me
Disconnect the o2 sensor. It force's the ecu into open loop. See if it makes a difference.
 

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Discussion Starter · #4 ·
You need to first figure out if it's fuel related or electrical. When it quits, check and see if you can hear the fuel pump cycle on for a couple seconds when you turn the key to the run position.
fuel pump does cycle on when I turn the key, it also cycles when I start cranking it so I know the CPS is working too
 

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A charge issue definitely can. Keep your eye on it and see if the voltage correlates to the problem when it happens.
I would think that you have a sensor issue though. Try this. Next time it happens disconnect the battery and let it sit for 10 seconds. Just a long 10 count. Hook it back up and see if it starts. If it does then maybe a bad crank sensor.
O2 trick is to force it into open loop and a default calibration. It will run rich but no big deal if it keeps you on the road. If it doesn't rehook up the battery and pull the battery cable for the 10 count to clear the codes.
No codes? So you don't see 12 and 55?
 

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Discussion Starter · #9 ·
A charge issue definitely can. Keep your eye on it and see if the voltage correlates to the problem when it happens.
I would think that you have a sensor issue though. Try this. Next time it happens disconnect the battery and let it sit for 10 seconds. Just a long 10 count. Hook it back up and see if it starts. If it does then maybe a bad crank sensor.
O2 trick is to force it into open loop and a default calibration. It will run rich but no big deal if it keeps you on the road. If it doesn't rehook up the battery and pull the battery cable for the 10 count to clear the codes.
No codes? So you don't see 12 and 55?
Yeah I've got 12 and 55 so I know the computer is still good
 

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I would think that you have a sensor issue though. Try this. Next time it happens disconnect the battery and let it sit for 10 seconds. Just a long 10 count. Hook it back up and see if it starts. If it does then maybe a bad crank sensor.
 

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Discussion Starter · #12 ·
My crank sensor is on the front of the engine where I can easily reach it, I can unplug that one instead if that's what you intend the battery unplug to do

Also I'm pretty sure it's heat related because when it dies, if I open the hood and let it cool off for 5 minutes or so it starts up fine

Also, my alternator gauge is reading 14v, if I turn on the heater it drops to 13-ish, is it supposed to be reading 14???
 

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My crank sensor is on the front of the engine where I can easily reach it, I can unplug that one instead if that's what you intend the battery unplug to do

Also I'm pretty sure it's heat related because when it dies, if I open the hood and let it cool off for 5 minutes or so it starts up fine

Also, my alternator gauge is reading 14v, if I turn on the heater it drops to 13-ish, is it supposed to be reading 14???
Yes.
 

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Discussion Starter · #14 ·
Alright so whatever the issue is, I know it must be heat related because the distance I can drive is proportional to how long I let the engine sit after it dies

I'm still thinking it's the alternator overheating, I have an electric fan and with it being summer it's running constantly
 

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Alright so whatever the issue is, I know it must be heat related because the distance I can drive is proportional to how long I let the engine sit after it dies

I'm still thinking it's the alternator overheating, I have an electric fan and with it being summer it's running constantly
The fan shouldn't be.on above 30'mph. Does the temp gage stay in normal range?
 

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Discussion Starter · #16 ·
It's an aftermarket electric fan, mine was originally belt driven

I have it set to come on at 215 (I think) and the temperature was always slightly over the center notch on my gauge, sometimes further right with all the uphills, sometimes on the right notch
 

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It's an aftermarket electric fan, mine was originally belt driven
Doesn't matter. The fan should be off above 30. Shut off the switch if it's sustained 30mph
 

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Off topic, but mine did the same thing i have a 91' yj 2.5 manual after 4 days of buying it for 5 grand it sputtered backfired an then died thought it was out of gas put gas in it still no crank tried putting starter fluid in the intake it would act like it was gonna crank but wouldnt after changing the fuel pump fuel filter regulator had the lines blown out i got fuel up to the rail but still no crank changed the position sensor rotor cap dis cap plugs an wires still no crank bought a new battery an new starter no crank finally i tried the ecu an didnt realize it was impossible to find one supposely there interchangable but ive called ecu rebuild places an they said its not so im confused mine sat up for 6 months or more an ive sunk every dang dollar into this rock
 

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Off topic, but mine did the same thing i have a 91' yj 2.5 manual after 4 days of buying it for 5 grand it sputtered backfired an then died thought it was out of gas put gas in it still no crank tried putting starter fluid in the intake it would act like it was gonna crank but wouldnt after changing the fuel pump fuel filter regulator had the lines blown out i got fuel up to the rail but still no crank changed the position sensor rotor cap dis cap plugs an wires still no crank bought a new battery an new starter no crank finally i tried the ecu an didnt realize it was impossible to find one supposely there interchangable but ive called ecu rebuild places an they said its not so im confused mine sat up for 6 months or more an ive sunk every dang dollar into this rock
Welcome to the forum.

You should really start your own thread. Because your issue is different from the OP's problem on this thread.

Also, punctuation really helps us understand what you're try to say.:highfive:
 
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