Complete and Utter failure!!

[Scamper]

When I first got the vehicle, the fuel sending unit was bad so the gas gauge didn't work. I did an initial test at high speed with rough driving and got ~24MPG. I then started driving as efficiently as I knew how, and figured I could drive ~250 miles without worrying about running out of gas. I've since replaced the sending unit and pump, and on a recent trip to my cousin's, ~200 miles...

I filled the tank at 155,272 on the odo, on the way there and back I pulse & glided, engine off coasted, and kept the radio quiet (I have some subwoofers in the trunk).

I filled up again, 155,482 on the odo, 8.515 gals. Very disappointing, ~24 MPG driving rough, ~24 MPG driving efficiently. Hmmph. I know this stuff works, I've gotten good mileage in other vehicles.

It does have an automatic, so I've been gentle on the throttle to keep engine speed down, would it be a good idea to try hard starts? Let the engine rap out 5000 RPM shifts.

I think, before further testing, I need to get my MPGuino hooked up. I've been having trouble identifying the correct wires.

[H-Man]

Don't EOC with an automatic, stuff breaks that way.
Check your plugs and thermostat.
You may need to power cycle the engine control computer, then while you have the cables off check them for corrosion. My car had the ground held on with a zip tie.

[Scamper]

Thanks. The plugs won't be easy to get to, the intake manifold covers half of them. I'll look into that and see what I get.