Okay I just replaced my dying old fuel pump with a new walbro 255lph. Took the car out on its first tank and I got just over 100 miles on the ENTIRE TANK! Came out to be 9.5 miles per gallon . I used to get about 13 MPG for referance...but what the hell? The exhaust does smell like its running rich. I also have a tune in the car, you think taking the chip out might help balance whats going on here? Right now I could give a hoot less about power, I'm driving this thing to North Carolina from New Mexico tommorow, thats 1900 miles. Any Ideas?

 

If the battery was disconnected, the ECM could possibly be going through relearn mode, so the first tank could give crap mileage. I've had my 15mpg drop to 9mpg, but went back up for the 2nd tank.

 

possible o2 sensor fault? you gotta change those things every 100,000 miles or so haha. do you have an afpr?

 

Stock FPR and new O2 sensor. I lost the milage immediatly after the fuel pump install.

 

Like I said above.

Same thing happened to me a few months ago, when my fuel pump was replaced.