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Popcorn missfire

Old wrench ?

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Old wrench ? Enthusiast

Old wrench ?

Posted
Posted

Greetings all. I have a1992 g3500 5.7. At idle and steady rpm she runs ok but has slight misfires not any one cylinder kinda like popcorn popping . Could it be a dripping injector (tbi)? 61000 miles. Fresh fuel .  Good tune up. Whats the best way to see tbi spray pattern?

Old wrench ? Enthusiast

Old wrench ?

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Thanks 4 reply. I replaced cap rotor wires plugs. Low milage 61000...500 last year. Just bought it. Kinda think its a dribiling injector. Or distibuter pickup. It had the corrosion virus on the coil wire to cap. Im going to give it a good freeway run tomorrow may be carbon on valves. Mite have to dig out more diagnostic stuff .

riverbanks Senior Enthusiast

riverbanks

Posted
Posted

Popcorn,sounds like stray spark,peak under cap?,damp?or to check spray pattern,use a flashlight while it's idling for a nice cone shape pattern and after shutdown for a leaker,wear safety glasses

Bigfutz Enthusiast

Bigfutz

Posted
Posted

If I’m understanding your description as popcorn being random and not evenly timed, I recently developed something similar on my 95 350 TBI. Mine seems to happen only when engine is warm, AC is on, and in Drive with the brakes on (at a traffic light for instance). It stumbles just briefly but randomly (like popcorn?). I was thinking something with the Idle Air Control (IAC)? Suggestions appreciated.

Old wrench ? Enthusiast

Old wrench ?

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'll

MThanks so much for replies and help. Tomorrow. I will check tbi spray. And a good drive. I will keep alll posted. Fyi. I am having problems with profile as. I whave no face nor do i tweet

Old wrench ? Enthusiast

Old wrench ?

Posted
  • Author
Posted

Greetings all. Today 103degrees waited 4 sun to go down. Earler i disconnected the "computer" to check connections looked good. Fired up noticeable improvement. Dug out the old OTC obd1 scanner. Data strean map volts +- .5 volt. Injector pulse kina bouncy computer compensating. So i ran it at 1500 rpm for 30 40 minutes. Very hot inside a van. ? . the map volts settled +- .2. Injector pulse fair ly steady. She is puuuring now??. My conclusion is super low miles61000 (500) last year. The old girl was carboned up particularly on intake valves. Thanks 2 all gm truckers who replied.

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