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4.3 issue

Old May 16th, 2019, 12:17 PM
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Default 4.3 issue

Thanks in advance for the help.

Recently bought a vehicle with a 4.3 tbi in it. Has mild cam.

Starts and idled well but hesitant and poor power under load.

Previous owner stated : ran excellenf until out mudding and blasted through a mud hole. Ever since then ran crappy
Took it home checked a bunch of things
Good compression
Good fuel pressure
Good map
Nonsign of spark arcing
Fuel spray pattern looks good
Pull plug wires one by one while running, same rpm drop for all. Seem equal, no dead cylinder.


Ok now the weird part
Checked timing (yes properly disconnecting timing wire) and found it to be a bit retarded. Advanced to correct spec run a bit better but still poor.
Continued advancing time until it runs nearly normal. Approximately 20 initial now. Starts and runs and accelerates good now.

Though 20 initial seems very excessive.

My thought is that he over revved it playing in the mud and skipped a toogh on the cam timing.
Likely to have crappy nylon timing gear

Racap
Only runs decent with way advanced intilal timing.
Ran fine until playing running it hard.

Thanks for the ideas

Last edited by 4.3jet; May 16th, 2019 at 12:22 PM.
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Old May 16th, 2019, 1:53 PM
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it does sound like something has slipped. but what year 4.3 are you working on?
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Old May 16th, 2019, 6:54 PM
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TBI 4.3
88-91ish
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