1998 GMC Jimmy Cuts out/stalls

Tiny
SMOKEJOHNSON
  • MEMBER
  • 1998 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 135,000 MILES
After 30 minutes of highway driving my motor starts to cut out, the max RPM that this happens at will steadily drop. If I pull over and shut the motor off it will run better for a few minutes before it starts happening again. Warmer outside temperatures seem to make the problem worst. I have found that if I ease into the throttle the RPM's will climb again but if I step on it the motor falls on it's face.

Here is a list of what I have tried so far:

air filter
fuel filter
throttle positioning sensor
mass air flow sensor
coil
ignition control module

I have also looked for vacuum leaks, I found none.
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Wednesday, March 24th, 2010 AT 7:29 PM

10 Replies

Tiny
JACK42
  • MEMBER
Could be a weak fuel pump, or partially plugged exhaust that builds up and causes thelack of power. Try loosening the ehxaust before the cat converters(at bottom of manifolds) and driving it. It will be loud, but if the cats are the problem it will retain its power. As far as fuel goes, you will need a manual pressur egauge to verify whether or not it has good pressure. At your mileage it could very well need a new fuel pump
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Thursday, March 25th, 2010 AT 7:53 AM
Tiny
SMOKEJOHNSON
  • MEMBER
Thank you Jack, I will try the exhaust test before replacing the fuel pump. Do you think the need to drive it, for say at least 30 minutes on the highway, before the problems starts will hurt anything in the test?

On a side note on the fuel pump. When I turn the key to "run" without starting the motor my fuel pump starts running like they all do. The difference is mine never shuts off. It will keep running for over a minute. I think it should only run for a few seconds and then shut off. Maybe it is the fuel pump?

Some more interesting facts, all temperatures are Fahrenheit and all temperatures are outside air.

*30 degrees - Noticeable but not really a problem

*50 degrees - It becomes an issue but is still manageable by pulling over and turning the motor off. Works better if you sit for a minute but just killing it and starting immediately helps.

*70 degrees - I probably should not be driving it since the lack of acceleration becomes a safety issue.

Warmer temps are right around the corner and I am freaking out, LOL. Any and all help is appreciated.

James
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Thursday, March 25th, 2010 AT 12:59 PM
Tiny
JACK42
  • MEMBER
That is odd the pump runs that long. If you have afuel pressure gauge, see how fast the line pressure bleeds down, this is one indicator of a bad fuel pump. The ambient temp usually messes with the MAF sensor more than anything, but that is already off the list. By running it that long, you may at most set an o2 sensor code from the "ehxaust leak" that you creat to let the gasses out, maybe a "catalyst efficiency" code too. But they wont change the way it runs
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Thursday, March 25th, 2010 AT 5:31 PM
Tiny
SMOKEJOHNSON
  • MEMBER
Thanks Jack. I will perform the exhaust test to see what happens. If that's not it I may just have to break down and pay a mechanic to check the fuel pressure/fuel pump. I will replace it myself but after checking the prices I want to know for sure before shelling out $300.

I'll let you know in a day or 2 what I find out.

James
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Thursday, March 25th, 2010 AT 7:22 PM
Tiny
SMOKEJOHNSON
  • MEMBER
Scratch 2 more things off the list. Created the exhaust leak this morning and took it for a test drive. Same problem occurs. While looking through my book I noticed a Intake Air Temperature sensor. Checked the resistance cold and then checked it again after the motor was warmed up and the resistance drops just like the book says it should.

Next on the list will be the fuel pump but like I said I think I am just going to have to pay a mechanic to check it out for me. Hopefully I can find someone to look at it this weekend.
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Saturday, March 27th, 2010 AT 10:36 AM
Tiny
2CARPROS LINSEY
  • MEMBER
Hi smokejohnson,

We hope you were able to resolve your problem with your jimmy. We thank you for your donation and look forward to helping you in the future. Let us know if there is anything else we can do to help.

Thanks again and have a great wekend!
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Friday, April 2nd, 2010 AT 1:39 PM
Tiny
SMOKEJOHNSON
  • MEMBER
Thanks Linsey.

I finally gave up and took the Jimmy to a mechanic Tuesday. I have not heard anything yet but when I do I will post what it was.

Great site, keep up the good work.
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+1
Friday, April 2nd, 2010 AT 4:44 PM
Tiny
2CARPROS LINSEY
  • MEMBER
Sounds good man, I hope it doesn;t cost you an arm and a leg. Let us know, Thanks again.
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Friday, April 9th, 2010 AT 12:57 PM
Tiny
SMOKEJOHNSON
  • MEMBER
Jack was right, it was a weak fuel pump. After everything was said and done I ended up paying $450 and she is running like a champ.

Thanks for the good advice :)
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Friday, April 9th, 2010 AT 6:44 PM
Tiny
JACK42
  • MEMBER
Im glad it hear you are back on the road
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Friday, April 9th, 2010 AT 8:49 PM

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