Rough Idle After WOT - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 3 (permalink) Old 05-19-2017, 05:31 AM Thread Starter
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Rough Idle After WOT

Title says it all. Doesn't matter if I'm in park or driving. If I goose it and let off the idle is very rough for maybe 60 seconds and slowly recovers. Maybe my vacuum secondary is too rich? Any input would be great.

1966 Galaxie
289 - Mostly stock
Holley Avenger 4bbl carb w/ RPM intake

Really haven't messed with anything before this started happening.

1966 Ford Galaxie 500 -289
2005 Ford Expedition -5.4
1983 Honda CM-450a -450cc
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post #2 of 3 (permalink) Old 05-19-2017, 06:49 AM
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Re: Rough Idle After WOT

Most likely the pump shot is a little high.
It's a balancing act, you need it to avoid a lean condition when opening the throttle rapidly, but the fuel needs to burn off when you let off it.

Also remember when opening the throttle quickly, vacuum drops and gasoline falls out of suspension, the pump shot helps cover this issue by shooting fuel into the incoming air stream.
When you let off the throttle rapidly the fuel that has fallen to the floor starts to vaporize again but due to the engine requirements dropping, it's running very rich.

Good luck

1976 F100 390/c6
1963.5 Galaxie 446FE/c6
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post #3 of 3 (permalink) Old 05-20-2017, 12:59 AM
Join Date: Jun 2006
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Re: Rough Idle After WOT

Bad power valve? It opens when you goose it, dumping extra gas into the intake. Maybe too much, and it takes a minute to burn off. I like your idea about the secondary better, though. Maybe the float is too high.

To every man upon this earth
Death cometh soon or late.

Putts drives a 1965 Galaxie. Rebuilt 390, 4100 on a Performer, MX, AC, PS, PB w Scarebird front discs on Cragar 17" S/S.
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