81 Ford f100 4.9 inline 6 dips rpm during idle sometimes dies. Possible problem?

Asked by Jonathan Nov 13, 2016 at 08:37 PM about the 1981 Ford F-100 Standard Cab LB

Question type: Maintenance & Repair

Hey I've been working on an 81 Ford f100 4.9 online
6 manual. She runs very well. The only issue I've
been having is that sometimes when I let it idle after
driving (usually about 30 minutes into the drive) it
sometimes stalls. This usually happens during stop
and go traffic or if I'm idling up slope on a hill. It
sounds like the engine is normal then the Rpms
drop very low and you can hear a low resonating
rumble. If I don't pump the gas while idling it
sometimes dies. I've emptied about an entire can
into the carb and replaced the air filter as well as
put some new oil. Any thing i can take care of
myself before I have to take it to a mechanic?

3 Answers


It may be time for a carburetor rebuild and a thorough maintenance check . You could try running some fuel system cleaner through it to see if it clears up, but depending on mileage, it may need something more extensive. what kind of choke is it equipped with? Make sure the linkage is free and operates smoothly.


Not sure how many miles are on it, but being 35 years old, if it is the original carb, there is a good chance the carb jets are worn badly. I would recommend a major rebuild or buy a factory rebuilt carb from one of the parts houses.

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