1994 Sierra 1500 5.7 Backfire and sputter

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1994 Sierra 1500 5.7 Backfire and sputter

Unread post by Tommyt15 » Sun May 12, 2013 12:16 am

Driving around town is fine but if I'm on the highway for more than 30 minutes my 1994 GMC K 1500 5.7 truck will start backfiring and lose power to where I have to pull off the road. For example: I was driving up hill and as soon as the truck down shifted it started sputtering and backfiring. I pulled off the road and the truck idled fine, would rev up fine with moderation but if I stomped the gas pedal it would sputter and backfire. I let the truck sit for an hour and drove home with no problems. Two weeks later the same thing happened again. The check engine light does not come on and the gauges read fine. The truck is currently running solid. Any Suggestions thank you in advance!

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Re: 1994 Sierra 1500 5.7 Backfire and sputter

Unread post by ProTech » Sun May 12, 2013 5:51 pm

Seems like something is getting hot and breaking down under load. This could be an ignition coil, distributor, ignition wires, pickup coil, plugs, etc. Possibly even a crank sensor (if equipped). You can try loading it up (brake torquing in gear) and try to determine where the issue is or what cylinder(s) are misfiring. The best way obviously would be to watching what is going on with a scanner.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

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