Mechanics

ENGINE MISS

Ford F-150

The truck is 91 ford F-150, 302, 4x4 manual. Bought the truck in rough shape. It idled and ran very badly, so replaced plugs, wires, cap, rotor, and fuel filter. Truck still wouldnt idle well, so replaced idle control module/ motor. When I push in clutch, engine will over rev, or drop rpms to near death levels still. Also, engine misses, fairly bad. In addition, chewing through fuel at alarming rate, about 6 mi per gal on rear, and far worse on front tank I think. No leak in line, good pressure at regulator. Confused as to what would cause the miss and poor fuel milage. Very obvious engine running VERY rich. Any suggestion?
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Drizzt_micheau
February 27, 2007.



Are you able to hook a code scanner up to it and see if the computer is setting any fault codes? If you don't pull anything up, I would then double check the basics first. Adequate fuel delivery, spark plugs firing at the right time. Check compression as well. (How many miles on the engine?)

Don't rely exclusively on the computer though. Being a '91, the computer won't pick up on what's about to fail, only what already has. So you could have a sensor or a solenoid way out of whack and the computer wouldn't know it. I hope this helps.

Tiny
Indyuke
Feb 27, 2007.
The truck had 130000 mi on it. I dont know about the trouble codes, but check engine light comes on after a few minutes of starting it, and that is where it starts to drive poorly. It is getting fuel, good fuel pressure, fresh tuneup with good spark, just timed. I have checked through everything on fuel system, except injectors. Would injectors sticking open cause it to dump fuel badly, miss, yet still run well enough to get up to 65?

Tiny
Drizzt_micheau
Feb 27, 2007.
Yes, a stuck injector will cause those symptoms. It will also cause the truck to run with a noticable " thub, thub, thub" with a constant poof of white steam out the tailpipe.

Possibly in this case, being able to scan the computer for fault codes will give you the clue you need to narrow down the problem. Since it's starts to perform poorly when the check engine light comes on, (that indicates fault code(s) was set) that would be an emission component related problem.

Tiny
Indyuke
Mar 2, 2007.
Thanks for the replies. It was a fuel pressure reg.

Tiny
Drizzt_micheau
Mar 7, 2007.