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post #1 of (permalink) Old 07-02-2007, 01:39 PM Thread Starter
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Jeep cutting out

When I am driving the Jeep will just stall for 1-5sec then start up again, with a surge. It happens primarily at low RPMs when I am starting off the line, and It did it 5 times while I was positioning to test my rear wheel on a stump yesterday. Though it happened today at 60mph on the freeway twice, and once at 30mph. I did notice the RPMs go to zero when it did it at 25mph Friday, though have had to concentrate on driving and was unable to look at my gauges the other times.

Additional Info:

I Have MPI. on the 4.2.
The fuel pump is 3 mos old.
The Fuel filter was changed then.
I have a cut out for the fuel pump, which the solenoid shorted last week, the CEL will go on if the fuel pump circuit is disconnected while running, the CEL has not gone on.
Starts up right after every cut out.
The radio does not miss a beat when this happens.
Has not happened at night, so can't say if the lights dim.
It seems to happen while cool, not so much at operating temp.
I have checked the wires, shook the wiring harness, no problems (except the O2 sensor wires seem to get too close to the belt and were worn open (fixed last night)).
Pretty much everything else is original MPI or rebuild 30k ago.

Any ideas? Anything I should check?

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #2 of (permalink) Old 07-02-2007, 02:04 PM
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Youíre either loosing voltage to the ignition or the sensor in your distributor is going bad as evidenced by the tach going to zero even though the engine is still turning. Something could be going to ground or it could be the module too.

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post #3 of (permalink) Old 07-03-2007, 08:25 PM Thread Starter
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Hey thanks Taz,

Yep, Cap and Rotor, I guess when you seal it without a breather, it can get pretty corroded.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #4 of (permalink) Old 07-03-2007, 08:31 PM
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Not what I was thinking and I donít know how that would make your tach go to zero. I hate to be the bearer of bad news but I donít think youíve found the whole problem yet.

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Those who understand binary and those who don't.
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post #5 of (permalink) Old 07-03-2007, 09:34 PM
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The engine can still be turning over and the tach read 0....What would tell me is that the signal to the tach is gone. On most engines this is the pulse to the coil to fire it. The tach is basically a frequency counter calibrated for the # of cylinders.

Yea, I agree with Taz, I don't think you have found it. The MPI system is pretty basic...CPS and TDC sensors basically run the engine. Everything else is there to fine tune the performance. If I remember correctly, once the engine has started, it does not need the TDC sensor in the dist....it runs off the CPS. But, if you loose the CPS...dead....the computer will stop all ignition activity.

I believe your CPS is down on the harmonic balancer. I would check it's mounting and break/make the connector a few times.

Scott...is your MPI OBDI? If so, I have an OBDI scanner...but we might need to get the Mopar connector...not sure if it is the same as the GM one...you are more than welcome to try it.

Otherwise, short out pins 1 and 2 and read the codes. You can sometimes have a code but it won't set the light.

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post #6 of (permalink) Old 07-03-2007, 09:51 PM Thread Starter
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Thanks guys,

Well it runs fine today. However, I will check the Crank sensor. It does not have a Obdi connector, but the ignition cycle starts the codes on the CEL. It thru a code of 12, which I didn't look up, since I am on my cell phone.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #7 of (permalink) Old 07-04-2007, 02:17 AM
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Switch to carburatuion,,, you will never regret it..... By the way I was drinking from your mug tonight,,, so you may or may not want to follow my advice,,,,,,, When you gonna drag your bitch ass to Indiana,,,, Ddawg out did you,, you need to man uppppp ...

Ya only go around once, best to enjoy it the first trip.
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post #8 of (permalink) Old 07-04-2007, 07:46 AM
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About 8 years ago my CJ would cut out on me -- the engine would just die. This typically occurred on left hand turns and hard acceleration. I could not figure it out until a couple of wires burned up. Apparently, a wire had enough movement in it and was shorting against the distributor. This would cause the motor to die. I have never had this problem since replacing that wire. This is also when I went through the wiring harness and replaced all of the masking tape that was used to "insulate" bare wires.

Skip forward about 3 years. I installed the Howell TBI. The motor would start to die on deceleration and hesitate on starts. It turns out that the idle air mixture needed to be adjusted. This essentially raised the RPMs a little. The motor has not died on me since -- other than stalling due to releasing the clutch too fast...

I don't know if either of these are similar to your situation or not.

-- Mike
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post #9 of (permalink) Old 07-04-2007, 10:42 AM
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Funny story about cutting out on turns.
A gal came into the shop one day complaining it would stall on left turns. She left it with us.
We tried and tried to get it to cut out - it ran fine. Nothing wrong that we could find.
When she came back I had her drive it to show me.

She put the key back on her keychain then showed me it stalled as we turned left out of the driveway.

Her heavy keychain with lots of keys would swing from the turn, and turn the ignition switch off! The detent in the switch was worn so much it turned freely.

Go figure!
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post #10 of (permalink) Old 07-04-2007, 11:47 AM
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Since we're onto funnies and oddities, when I was high school there was a rumor going around that an elderly English teacher had complained about the fuel consumption of her new Beetle. In several visits the dealer couldn't find anything wrong, so they went for a ride with her. She got in, pulled out the choke, hung her purse on the knob and started to drive away.

EVERYTHING's easy for the guy who doesn't have to do it.
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