Why won’t my truck idle

Asked by Hunter Jul 27, 2023 at 07:24 PM about the 1979 Ford F-150 Custom RWD

Question type: Maintenance & Repair

I have a 79 Ford f150 with the 390 motor in it I
can crank it right up and take it down the rode
no problem but when I got to stop at a stop sign
or slow down it will die it won’t idle sitting still by
itself I have ti keep the gas pressed down and
the brake so it won’t die what would be causing
this

1 Answer

157,465

Sounds like a carburetor problem. Make sure the choke plate, on the top of the carburetor is fully open when the engine is warmed up. Remove your spark plugs and look at the electrodes. Are they black and sooty! If so that's an overly rich air to fuel mixture. Too much gasoline and/or not enough air. Are the electrodes white? If so you have an overly lean air to fuel mixture. Too much air and/or not enough gasoline. Also check the EGR valve, if equipped. If it's not closing all the way you will have a no idle/stalling condition. Remove the EGR valve and clean it. Make sure it's closing properly. If, after you've cleaned it it's not closing properly it'll have to be replaced. Hope that helps! Jim

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