Yukon is cutting out please help

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99whiteyukon

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Hello I have a 96 GMC Yukon with the 5.7. In the mornings it will run smoothly for about 1 mile then starts cutting out and backfiring in low rpm then you can stomp down on it and it runs great. Throughout the day it smoothes out a bunch it is worse in the mornings. I have new plugs, wires, cap, and rotor and coil also. It threw a code once and it was random misfire what would cause this???
 

RonH

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Is it showing any codes? If the Service Engine light is not lighted, you might get autozone or another store to check to see if there are any pending codes.

You might also want to check the throttle body for gunk buildup under the valve plate. Couldn't hurt to clean it thoroughly anyway.
 

mightymouse

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I had this problem a while back.
I would bet it is your catalitic converters, O2 sensors, or a
combination of the two.
Drive it at night getting it up to operating temps.
Stop and get out and look at the converters.
If they are glowing red, they are restrictive causing the 02
sensors to miss read, causing said random missfire.

Hope this helps.
 
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