Wierdness....

[SanDiegoExplr]

Lately I've been noticing a pretty significant drop in power (mainly in the low rpm range it seems) and a HUGE gain in gas mileage. I havent really changed my driving style or anything. Before I was gettin like 220 miles to a tank. Now im gettin like at least 270 easy. Whats goin on here?

 

[mosinman]

Don't know. things like fuel pump, clogged fuel filter, or a computer problem maybe??? I would think those problems would cause more driveability symptoms.

 

[aldive]

Have you run a fuel pressure test?

 

[SanDiegoExplr]

no i havent. how would i go about doing that? and what would it tell me?

 

[oceanworker]

On the 4.0, attach a fuel pressure gauge to the Schraeder vavle which is on the plenum (just above and between the heads), on the passenger side of the air manifold. It should be next to the fuel pressure regulator.
You need to take a reading with KEY ON, ENGINE OFF to get your first reading. When you turn your ignition key to ON, you should hear the electric fuel pump engage.
Then take a reading with the engine started at idle. I don't have the exact spec., but the pressure should be LOWER with the engine running. Search this board w/ "fuel pressure" to find some good posts.