Expert: Dusty Granata - 6/22/2009

Question
I have a 1986 ford F-150 with a 302 EFI engine.  It starts hard, mainly when it's cold but still not that easy when it is warm.  Also under acceleration it bucks or hesitates, I have replaced the plugs, plug wires, battery, air filter, pcv valve, idle air control valve, throttle position sensor, fuel pump, and fuel filter.  Still having problems, not as bad as they where but still there.  I have run out of options and would appreciate any help.  Thank you

Answer
Hi Matt, by the sounds of your truck’s symptoms I would say you may have more then one single problem. There are a few things I would suggest to you, but first make sure that you put a new fuel filter in, I have seen a few trucks that had similar symptoms and it was a badly plugged fuel filter, also while you’re at it, check your air filter.
Judging by your description you may have a fuel injector problem, it may be one bad injector, or it could be a hair off time, and as 1986 (first year for EFI if memory serves) through 1992 F-Series use vacuum advance timing. If your initial timing is advanced or retarded too much it may cause bucking. Check your vacuum hoses, a bad or leaking vacuum line can cause all sorts of havoc, from an extremely high idle speed to a No-Start condition. You may also want to check the fuel pump on the frame. It is located almost perfectly inline with the headlight foot switch on the floor, on the inside driver side frame rail.