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Old 06-30-2016, 12:25 PM
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Stop me if you've heard this one before...

So I finally gave up trying to be a Youtube/Google mechanic for the issue I've been having for the last couple of months, and enlisted help from YourMechanic.

A little background...a couple of months ago, my '91 2.5L would seemingly try to stall out, then rev high, then back to normal idle. It was an intermittent problem that I just threw parts at. Two TPSs, an O2 sensor, a fuel filter, direct spray SeaFoam into the throttle body, cleaning & tightening fuel pump ground & battery grounds. Nothing seemed to work, aside from 2 days post-ground cleaning & tightening, but the problem returned.

Fast forward to this past weekend when I changed spark plugs, wires, distributor cap & rotor, and replaced the valve cover gasket. Still nothing worked, so yesterday I found the YourMechanic website, accidentally, before purchasing a new ECM in a last-ditch effort to correct the issue.

20 minutes before the guy arrives, I go to move the Jeep & she runs terrible, but I get her moved. I realize my garage door opener is in the way & try to start it again...no dice. She tries to crank but never starts...first time that's happened. So I push the Jeep a few inches forward & try the key again...nothing...no check engine light & no fuel pump priming. I'm thinking this is actually a good thing since I have a mechanic 15 minutes away.

And then he shows up. Jeep starts without issue and NEVER TRIES TO DIE. The problem is completely gone. We couldn't reproduce the issue that had been plaguing me for 2 months straight without fail. We fiddled for 2 hours...he checked fuel pressure (fine), ran codes (fine) and took for a few mile test drive. NOTHING. It's like my Jeep just decided since there was a mechanic close, she needed to be on her best behavior.

I drove her 25 miles to work after the (wasted) $70 inspection with no issue. It makes no sense, but for now, I have my baby back & I'm happy. Completely befuddled, but happy.

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Old 06-30-2016, 01:02 PM   #2
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The boogeyman must have flipped some switch.

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Build thread for OJ, my YJ. 1993 Wrangler S 2.5L/AX-5/NP231 with SYE, Spartan locked Dana 30/Aussie locked Ford 8.8 @ 4.88, SOA lift with 2.5" OME HD springs and front Bilstein/rear Rancho shocks, Barricade 9500 winch, custom front and rear bumpers, 136 amp alternator, 35" Super Swamper LTBs.
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Old 06-30-2016, 02:36 PM   #3
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Gremlins!
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Old 06-30-2016, 04:12 PM   #4
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OJS-old jeep syndrom lol, that's wierd bro.
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Old 06-30-2016, 05:03 PM
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Really weird and it's got me spooked to go on any long trip since nothing was changed for it to start behaving.
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Old 06-30-2016, 09:24 PM   #6
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Haha stay within 15 minutes from home and drive on roads with shoulders for the next week.
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Build thread for OJ, my YJ. 1993 Wrangler S 2.5L/AX-5/NP231 with SYE, Spartan locked Dana 30/Aussie locked Ford 8.8 @ 4.88, SOA lift with 2.5" OME HD springs and front Bilstein/rear Rancho shocks, Barricade 9500 winch, custom front and rear bumpers, 136 amp alternator, 35" Super Swamper LTBs.
1999 Ford F-250 Super Duty 7.3L Powerstroke, single turbo, 6 speed manual.
Jeep manuals!
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Old 07-01-2016, 12:50 PM
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It died last night on the way home suddenly. Got it started after a few tries, and pulled into the gas station to fill up. When I got ready to leave, it was dead again. No check engine light, but it had plenty of juice. waited a few minutes & it started right up. Didn't have a problem until mid morning today when I had to do a Lowe's run for the plant. Came out & same thing...wouldn't start, no check engine light. Turned the key all the way off, tried again & it was fine.

I've gotta have a loose power connection to the ECM, or my ECM is going bad. Thoughts?
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Old 07-01-2016, 02:36 PM   #8
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Wow that is an odd situation. Have you drained the gas tank to see if there is anything that is getting sucked up in the filter then when it drains it gets fuel for a while again until it clogs?
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Old 07-01-2016, 02:36 PM   #9
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The check engine light should come on when the key is turned to on, about the same duration as the seat belt buzzer or fuel pump. If it does not illuminate, you have a blown capacitor in the PCM.
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Build thread for OJ, my YJ. 1993 Wrangler S 2.5L/AX-5/NP231 with SYE, Spartan locked Dana 30/Aussie locked Ford 8.8 @ 4.88, SOA lift with 2.5" OME HD springs and front Bilstein/rear Rancho shocks, Barricade 9500 winch, custom front and rear bumpers, 136 amp alternator, 35" Super Swamper LTBs.
1999 Ford F-250 Super Duty 7.3L Powerstroke, single turbo, 6 speed manual.
Jeep manuals!
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Old 07-01-2016, 04:04 PM
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Quote:
Originally Posted by MudMagnetYJ View Post
The check engine light should come on when the key is turned to on, about the same duration as the seat belt buzzer or fuel pump. If it does not illuminate, you have a blown capacitor in the PCM.
It's intermittent, which makes me think a short or bad ground rather than a blown capacitor.
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Old 07-02-2016, 08:29 AM   #11
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My bet is on bad ground somewhere, possibly to your fuel pump. But this is just by reading your thread. Gl! Gremlins are a pita
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Old 07-02-2016, 10:42 AM   #12
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add a couple new grounds one from battery to block one from battery to body and see what happens. also even if the ground visually looks good clean it with a wire brush or wire wheel. i had a toyota kill me random no start smack starter started right up ok bad starter- replaced starter same issue. cleaned all the grounds really well and havent had a problem since. i wouldnt throw a pcm at it without being 100% sure
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Old 07-06-2016, 08:46 PM   #13
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Quote:
Originally Posted by jwolfpack02 View Post
It died last night on the way home suddenly. Got it started after a few tries, and pulled into the gas station to fill up. When I got ready to leave, it was dead again. No check engine light, but it had plenty of juice. waited a few minutes & it started right up. Didn't have a problem until mid morning today when I had to do a Lowe's run for the plant. Came out & same thing...wouldn't start, no check engine light. Turned the key all the way off, tried again & it was fine.

I've gotta have a loose power connection to the ECM, or my ECM is going bad. Thoughts?
I highlighted in red one of your statements. What exactly does that mean?

Did you have a no-crank or a cranks but doesn't start condition?

A no-crank but works when fiddled with scenario leads me to the ignition switch, the cranks but not starts until after cooled off would have me replacing the relatively inexpensive coil or CPS.

Or, you might need to move your garage door opener again? Just for sake of repeating the better luck you had last time you moved it.
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Old 07-10-2016, 10:15 AM   #14
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Does the fuel pump come in with the key in before start?

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Old 07-14-2016, 12:01 PM
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Sorry for the delayed response. The fuel pump does come on with the key in before start when the CEL lights as it should. When it doesn't, no fuel pump activity.

I've narrowed to ECM - either a bad connection/wire, bad ground or ECM going bad. I'm going to check the wires & connections & grounds to see if it's (hopefully) that. I don't want to buy a new ECM unless I absolutely have to.
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Old 08-02-2016, 10:47 AM
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Quote:
Originally Posted by DryCreek View Post
I highlighted in red one of your statements. What exactly does that mean?

Did you have a no-crank or a cranks but doesn't start condition?

A no-crank but works when fiddled with scenario leads me to the ignition switch, the cranks but not starts until after cooled off would have me replacing the relatively inexpensive coil or CPS.

Or, you might need to move your garage door opener again? Just for sake of repeating the better luck you had last time you moved it.
It's a crank but doesn't start condition. It runs fine and then just dies with no warning. Sometimes it cranks & starts right back up without issue. Other times it cranks, but no start. On those occasions, the check engine light doesn't light when cranking.

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