89 F-250 5.8 4x4 Runs rough

Asked by brownlon Mar 17, 2017 at 07:47 PM about the 1989 Ford F-250 STD Extended Cab 4WD LB HD

Question type: Maintenance & Repair

As i was driving it the truck kept losing power. Finally got to a point it
wouldn't run to move it. The hose from EGR down to exhaust blew apart. I
have replaced that.... converter isn't plugged. We have replaced oxygen
sensor, MAP sensor, EGR.  We have new fuel pump, the correct fuel
pressure. Truck will start and stay running now but rough. Plugs if pulled
will be wet like it is flooding out but when we add carb cleaner it smoothes
out and runs fine. Any suggestions on why it would run so rough? Like the
fuel to oxygen level is out of balance..... what else could we check?

5 Answers
220,975

Rowefast answered 7 years ago

Check for vacuum leaks. Use some carburetor spray cleaner, and spray along the intake manifold gasket, and the throttle body base gasket, you would notice a change with the rpms of the engine.

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F_O_R answered 7 years ago

If all else fails, check the compression. Maybe you have a worn engine or a bad cylinder.

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220,975

Rowefast answered 7 years ago

Could be the fuel regulator. It still would start up. You can test that in place with the engine running by hooking up a fuel pressure gauge, then pull the vacuum line off of the fuel regulator. The fuel pressure should rise about 5 to 8 lbs. Also rev the engine up and see if it holds the proper fuel pressure.

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Guru995Z6J answered 3 years ago

I know this is old but....1992 F250 with 5.8 is driving me crazy! I have changed injector. Every sensor I could think of changed. Had vacuum checked. Changed everything else that I would have thought to cause my issue but my truck still is flooding and fuel economy is down by half.

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