89 F-250 5.8 4x4 Runs rough

Asked by 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?

4 Answers


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.

Gaskets have been replaced....all vacuum lines seem to be ok.


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


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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