My 1986 F150 5.0 EFI is hard to start when cold and bucks and jumps when warm, why?

Asked by RoyF Aug 22, 2014 at 05:09 PM about the 1986 Ford F-150 XL Standard Cab LB

Question type: Maintenance & Repair

Have replaced EGRw/solenoid, TPS sensor, IAT sensor, thermostat, plugs, distributor cap and rotor. Checked fuel pressure and was fine, but not while driving when bucking occurs. Starts fine once the truck has been started. Runs very rich, checked timing w/ spout disconnected. Any clues?

3 Answers
545

aarona74 answered 10 years ago

I have that same problem with my 92 f150 5.0 efi somebody PLEASE HELP US. I installed new vacuum lines which helped a lot but not completely. Running really rich and gas mileage is horrible... I'm getting about 5-7 miles a gallon. Thanks

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jrvilla67 answered 10 years ago

I had same problem with other problems , new oxygen or 02 sensor improved problem a lot ,still have unstable idle problem. i have 4.9 l inline 6 engine.

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2,665

Lance answered 9 years ago

Do a self check and pull the computer codes. Let us know what you get.

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