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Discussion Starter #1
I have a 1996 GMC Jimmy and when the truck shifts into 3rd gear there is some hesitation and sputtering...usually around 40mph. When I accelerate up to around 55-60mph the hesitation goes away. What could be causing this? A transmission going bad, maybe? I don't really notice any other problems, the truck shifts from gear to gear just fine and there is no real jerking or lag when I shift into drive. The truck has 240,000 miles on it. Any help would be greatly appreciated!
 

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Are you actually feeling the engine missing/sputtering or are you feeling this in the transmission like the torque convertor clutch trying to lock up & unlock? aka torque convertor chug
 

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Discussion Starter #3
It actually feels like the engine is missing/sputtering because you can hear it.....if that makes any sense.
 

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It's difficult to tell you where to start then because what's making it miss at 40-45mph should also make it miss at 55. The only thing I can think of is that the EGR valve might not be closing (it's only suppose to be open in mid range) & is possibly causing a lean condition that allows the missing under the lower rpms just after it shifts into high. Pull the egr & look inside at the valve & see if it's closed & completely seated. See if there's any carbon build up on it. If there is, clean it off so the valve can seat. I don't think this problem is basic tune up issues like plugs, wires, fuel filter, cuz these should affect it all the time, & moreso at faster speeds & more load when you need more fuel & spark, not just after shifting into high gear, but if not the EGR valve, then you might go ahead & take a look at them next.
 
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