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Miss firing at higher RPM

C

cgentile

New member
4.3L vortec
engine starts to

4.3L vortec
engine starts to miss fire on cylinders when opened up.. or running over 3800 rpm .
idles fine and then starts loosing power under load.. no rea Back firing just loss of power... more of a not running on all cylinders and never does this on lower speeds.
?
 
"Could be loss of spark or a f

"Could be loss of spark or a fuel restriction. Take a timing light on the next trip and check a few wires when it acts up. if you have spark testers, you can do multiple cylinders at once. If the spark is still there, look for a fuel restriction."
 
What year? Check each plug wi

What year? Check each plug wire on both ends to see if they are connected tightly. One recent poster found his similar problem was one loose wire on a plug that did just what you describe.
 
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