Engine shuts off while driving

1994 GMC SIERRA
250,000 MILES • 7.5L • V8 • 4WD • AUTOMATIC
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KURT2913
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Truck (1500, 5.7 liter engine) starts no problem, but after warming up about ten minutes the rpms drop and go back for about three minutes then shuts off. It will immediately start right back up. When you drive it it will start stalling when you get up to about twenty mph then you have to feather the gas to get back home. I have changed spark plugs and wires, oil filter, oil, coolant, sensor switch, distributor cap, rotor, ignition coil, throttle position sensor, MAP sensor and still runs the same. I am out of money and ideas.
Mar 28, 2018 at 6:53 PM
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STRAILER
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Hello,

Lets start by running the codes. Here is a guide:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

It sounds like you have a vacuum leak which these engine had at the throttle body gasket at the back. Try this guide to see if you can find it.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken
Mar 30, 2018 at 11:27 AM
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KURT2913
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I checked for vacume leak and can not find any. The truck starts fine but when you drive it down the road and give it 1/4 throttle it stumbles and back fires still
Apr 4, 2018 at 6:06 PM
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STRAILER
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Hmm that says to me low fuel pressure or bad MAP here is a guide and a diagram to help you see whats going on.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and

https://www.2carpros.com/articles/engine-backfires-while-running

Check out the diagrams (Below)

Please let us know what you find.

Cheers, Ken
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Apr 4, 2018 at 7:31 PM
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KURT2913
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So yesterday I put a new fuel filter in it and drove it around 3 miles and back and no issues. I left again in my truck about 30 minutes later and as soon as I pulled out right back to the back firing problem again. Can't give it any throttle to get down the road without backfiring. I'm not understanding why it didn't do it when I test drove it but then turned around 30 minutes later and started doing it again
Apr 7, 2018 at 5:50 AM
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STRAILER
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Sorry I didn't think of this earlier but have you changed the ignition module? Here is a guide to help you see what you are in for when changing the unit out.

I would also do the pick up use AC Delco

Please let us know what happens.

Cheers, Ken
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Apr 7, 2018 at 12:22 PM
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KURT2913
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Ok I just picked up the new ignition control module and getting ready to install it now. I'm praying its the problem. I will let you no how it turns out
Apr 8, 2018 at 10:48 AM
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STRAILER
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Me too, I have done a bunch over the years.
Apr 9, 2018 at 9:54 AM
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KURT2913
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I put the new ignition sensor module in and the truck ran fine all day. Thank you so much for your help
Apr 9, 2018 at 11:12 PM
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STRAILER
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Good to hear, please use 2CarPros anytime we are here to help.

Cheers, Ken
Apr 10, 2018 at 10:30 AM