Fast idle issues

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Jun 9, 2018 | 02:48 PM

442tom

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Joined: Jun 2018

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Fast idle issues

Looking at a 1978 Ranger with 351M. Truck idles nicely in park but revs high in drive. A tap of the pedal settles it down, but wondering what I might be dealing with; vacuum leak, choke problem or timing chain (had a car once that had a bad timing chain that caused fast idle). Any ideas? Thanks!

Last edited by 442tom; Jun 9, 2018 at 02:49 PM. Reason: “Isle” should be “idle”

Jun 9, 2018 | 03:20 PM

niko20

More Turbo

Joined: Feb 2018

Posts: 710

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From: Oregon

Maybe a vacuum advance issue? Although I would expect it to behave the other way around if so....does it have a stock carb?

Jun 9, 2018 | 03:25 PM

442tom

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No - Edelbrock 4 bbl.

Jun 9, 2018 | 04:43 PM

ranger140892

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Does carb have a good double throttle return spring? I'm surprised at times when I see guys running no throttle return spring at all. Could be sticky throttle linkage or butterflies. I'd spray it down really good with carb cleaner, inside and out, while working the throttle and secondary butterflies. Let it sit 15 min or so before cranking. then try it. If I bought it, that carb would come off and get totally disassembled and rebuilt anyway.

Jun 10, 2018 | 09:16 AM

meangreen92

Logistics Pro

Joined: Jul 2005

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Is the choke staying fully open upon warm-up? It sounds like your fast idle is kicking in when it shouldn't. Is the choke electric? Is it connected? Do those have provisions for the hot air tube which 'connects' to the manifold?