1994 GMC Sierra Stumble When Warm

1994 GMC SIERRA
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1994 GMC Sierra 4.3L V6 200,000 miles
I have been experiencing an intermitent hesitation or stumble in my truck. In park idle seems fine. When cold runs fine. When warm, problem occurs sometimes, and beginning to happen more often. Happens stopped in drive gear, or when at constant speed, but most often and noticable when accelerating. Replaced plugs, wires, fuel filter, O2 sensor, PCV valve, EGR solenoid and valve recently. Distributor, rotor, and fuel pump 40k old. Also, the air filter was covered in gas. Checked timing: at 8 degrees BTD ECM plugged in with +/- 2 degree "wobble" at idle.
Feb 25, 2007 at 10:23 AM
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CHEVY22
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is the enginelight on??

jim
Feb 25, 2007 at 10:26 AM
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intermittently, but when it was i got a code 32, which is why i replaced the EGR valve and solenoid. Haven't drove it long enough to see if comes back on again.
Feb 25, 2007 at 11:31 AM
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CHEVY22
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you should be ok unless there is a carbob buildup in the intake

jim

oh and leave some feedback if you were happy with your help , we all donate our time here helping others free of charge
Feb 25, 2007 at 11:45 AM
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So, the carbon build up might explain why i'm still getting the hesitation/stumble? I used a paperclip to clean out the EGR passage as suggested in answer to another question. Next step, remove, clean, and replace gasket for intake manifold?
Feb 25, 2007 at 11:57 AM
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CHEVY22
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at least check the passaged , the intake can really get gummed up inside so bad that i have just replaced them before ,

let me know

jim
Feb 25, 2007 at 12:19 PM
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found that i was leaking antifreeze from intake. Replaced the intake manifold gasket this weekend, and the stumbling is gone. check enginge light doesn't come on either, but i don't know if that was from replacing the EGR solenoid and valve or the gasket.
Mar 12, 2007 at 11:39 AM
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CHEVY22
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could have been a combination of both , glad it worked out

Jim
Mar 12, 2007 at 11:45 AM

Suggested Repair

Check the EGR passages and intake for heavy carbon buildup. Also inspect for a coolant leak at the intake manifold and replace the intake manifold gasket if it is leaking. In this case, replacing the intake gasket after earlier EGR work stopped the stumble and the check-engine light.

Conversation Summary

A 1994 GMC Sierra 4.3L had an intermittent warm stumble or hesitation, most noticeable during acceleration, with an intermittent code 32. Plugs, wires, fuel filter, oxygen sensor, PCV valve, and EGR parts had already been replaced. The expert suggested checking for carbon buildup in the intake and EGR passages. The owner then found an antifreeze leak at the intake, replaced the intake manifold gasket, and reported that the stumble and check-engine light were gone. The expert said both the EGR repairs and gasket replacement may have contributed.

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