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Unread 06-18-2013, 05:27 AM   #1
B_Baity10
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I have a 98 jeep grand Cherokee Laredo and whenever I crank it it will cut right off. Sometimes I'll get going down the road and then It will cut off. It cranks right back up after it cuts off though. I've already had the computer replaced in it.
Any ideas as to what else I could try?

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Unread 06-18-2013, 06:25 AM   #2
micifus
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How old is the battery? Jeeps do strange things when the battery gets low. Do any lights come up on the dash after it cuts out?
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Unread 06-18-2013, 06:26 AM   #3
dellis
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It would help to fill out your vehicle's profile.

Seriously, it can be dozens of things. There are some things that people recommend all the time (fuel pump, crankcase position sensor, and PCM), but it could be one of three dozen things.

Before you start throwing parts at the problem, three questions:

(1) When you say you replaced the computer, was it remanufactured, a used junkyard or eBay item, or from one of those dealers that cleans and polishes the exterior and then resells?

(2) A stall or no start is caused by no/low fuel, no/intermittent spark, timing, or mechanical issues. What testing have you done?

(3) What repairs have you tried other than the PCM? And, what parts did you use in the repair?
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Unread 06-18-2013, 06:39 AM   #4
B_Baity10
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Quote:
Originally Posted by micifus
How old is the battery? Jeeps do strange things when the battery gets low. Do any lights come up on the dash after it cuts out?
The battery is maybe 3 months old
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Unread 06-18-2013, 06:42 AM   #5
B_Baity10
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Quote:
Originally Posted by dellis
It would help to fill out your vehicle's profile.

Seriously, it can be dozens of things. There are some things that people recommend all the time (fuel pump, crankcase position sensor, and PCM), but it could be one of three dozen things.

Before you start throwing parts at the problem, three questions:

(1) When you say you replaced the computer, was it remanufactured, a used junkyard or eBay item, or from one of those dealers that cleans and polishes the exterior and then resells?

(2) A stall or no start is caused by no/low fuel, no/intermittent spark, timing, or mechanical issues. What testing have you done?

(3) What repairs have you tried other than the PCM? And, what parts did you use in the repair?
The PCM was $800 from California so I highly doubt it was from a junk yard.
I've replaced the alternator, the throttle position sensor and had all the wiring re done to the alternator
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Unread 06-18-2013, 06:48 AM   #6
B_Baity10
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Quote:
Originally Posted by B_Baity10

The battery is maybe 3 months old
No lights come on when it cuts off. The only way you can tell it cuts off is because the power steering an brakes go out and the engine dies but the radio and lights and everything else still work
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Unread 06-18-2013, 07:06 AM   #7
B_Baity10
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Quote:
Originally Posted by B_Baity10

The PCM was $800 from California so I highly doubt it was from a junk yard.
I've replaced the alternator, the throttle position sensor and had all the wiring re done to the alternator
I've also replaced the throttle body sensor and the ignition coil
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Unread 06-18-2013, 08:13 AM   #8
dellis
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(1) You are replacing a lot of "spark" related parts. So, does this mean that you know the problem is "spark" related? Were there codes you read from an ODBII scanner? Given what you are replacing - battery, alternator, coil, PCM, wiring - it seems like you suspect spark cut-out or someone read a P0351.

(2) If you don't "know" it to be a spark problem, another common issue of cut-offs is a fuel issue (pump or filter). Have you placed a fuel pressure gauge on the rail and observed behavior during your stalls?
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Unread 06-18-2013, 08:30 AM   #9
B_Baity10
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Yes those are what came up on the scan.

No I haven't tried the fuel gauge yet.
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Unread 06-18-2013, 08:47 AM   #10
dellis
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If it were my Jeep, I would put a fuel gauge on it just to rule that out.

If you saw a P0351, then I'm pretty sure that this is set when the PCM coil driver notices that there is not spark. Here's some things it could be ...
  • Your PCM is bad. Now, if you have replaced your PCM with no change in behavior, then you can rule this out ... if you had the problem a long time ago, then it went away after replacing the PCM, then it is now returning. Well ... it could be the PCM again.
  • Your Crankshaft Position Sensor is cutting out on you ... the PCM will shut down the engine if this sensor cuts out, and failures can happen after 100,000 miles. My observation, however, is that most people who have a failed Crankshaft Position Sensor can not even get their Jeep started.
  • You have bad wiring somewhere (broken/shorting/etc) ... jiggling the wire harness will tend to reproduce the cut-off problem.
  • You have a short or a voltage problem somewhere on the +5 supply from Connector #1. The +5 voltage on a '98 supplies the MAP sensor, the Crankshaft Position Sensor, the Camshaft Position Sensor, the and the TPS. I'm not sure if the +5 of Connector #1 is isolated from that of Connector #2, but the +5 of connector #2 goes to the Transmission Solenoid and the Speed Sensor.
  • The ASD relay is having erratic operation. These can get weak over time. An easy test is to switch the horn relay with the ASD relay.
  • It is rare, but if you have installed some of those fancy new spark plugs - something other than a simple copper one - they can create voltage spikes when they fire, and these travel back through to the PCM's coil driver and the 12 volt supply. It can cause a PCM to reset. Your PCM was designed during a time when spark plugs were just simple things ... your Jeep'[s PCM just needs things to stay simple and OEM.
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Unread 06-18-2013, 09:10 AM   #11
B_Baity10
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Thanks for the help!
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Unread 06-18-2013, 12:26 PM   #12
Oldfrog
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Zeejay has a list of 12 things to check when you have a stalling issue.

My latest stalling issue was a little oil and crud under my distr. cap ( under the cam sensor plate too)....OR....the coil wire that was crossing a plug wire as it was leaving the distr. cap.

Crappy batteries and/or connections will cause it too. Pay particular attention to all the grounding points, especially the one at the coil and the other below the oil dipstick.
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Unread 06-18-2013, 07:55 PM   #13
ZeeJay1997
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^^ this

and this
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V
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