What could cause this?

Asked by Guru94QP6Q Sep 17, 2020 at 11:31 PM about the 1992 Ford F-150 S LB

Question type: Maintenance & Repair

92 f150 5.0 when I give truck gas it wants to die.
Sometimes it wont even start. I've got black smoke
from exhaust. I've replaced throttle position sensor,
fuel pressure regulator, fuel pump, fuel filter, map
sensor, coil, wires, plugs, cap, button. Have
checked for vaccum leaks and have found none.
Truck ran great for about a week after replacing
fuel pump but is now acting up again.

1 Answer

Black smoke is a good indicator of a very rich condition. "Unburned fuel" By pulling the spark plugs one by one, there should be a very visible sign of excessive fuel on one or multiple spark plugs. Any cylinder that is fuel rich can potential be from a stuck open / leaking fuel injector or injectors. Its not the easiest thing to deal with , but hopefully that can point you in a positive direction.

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