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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

HELP stalling when decelerating / quick RPM drop

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Old Dec 28, 2015 | 03:31 PM
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86FordF150Philly's Avatar
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HELP stalling when decelerating / quick RPM drop

Hey guys need some help solving this one. 86 F150 4.9L I6, carb'd + manual.

To start, I was stuck behind an accident and led me to miscalculate gas for first time. Few days later ran low/out and it died. Sure I sucked some unwanted sludge up as truck had sat some before PO started making repairs.

The truck has been running great until then, now it has started doing something it has never done before. When the rpm's drop to idle the truck will stall. It does this going down the road and you pull up to a light, stop sign or slow for a turn. The truck does restart easily and maintains idle till you let the rpm's fall rapidly. You can prevent it from stalling by feathering the throttle allowing the rpm's to drop slowly.

I replaced the old, dirty fuel filter and it's running better but problem still around. Replaced cap, rotor, plugs and wire recently. Found a similar post in diesel forum but their 'fix' wouldn't apply here:
https://www.ford-trucks.com/forums/1...l-to-idle.html

Any thoughts / suggestions? Need to get her back out on the road!
 
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Old Dec 28, 2015 | 03:40 PM
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From: O-O-O-Oreilly's
Test/clean/replace your IAC.
 
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Old Dec 30, 2015 | 10:48 AM
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Originally Posted by mountain dewd
Test/clean/replace your IAC.
Where is that located? Having trouble finding it in Haynes manual, thanks again
 
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Old Dec 30, 2015 | 03:44 PM
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IAC == Idle Air Control valve which the EFI variants have and that didn't start until 1987, the OP is gonna have a feedback carburetor.
 
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