Mac_

I'm trying to work through a drop in the mpg in my 92 F-150. 5.0, 4 spd auto with overdrive, towing package, x cab.

Recently, if I don't let it warm up at least 3-4 minutes when it's cold, it will stall and then not restart unless I let it sit for about 15 minutes as though its flooded. So, if it is running rich for some reason, that would certainly reduce the mileage.

Any and all advice would be greatly appreciated. I'll post codes as soon as I get them.

Here's my game plan:

(1) Stop by Auto Zone and ask them to pull all current codes.

(2) New air filter, plugs.

(3) Get a vacuum guage and check for vacuum leaks.

(4) Check the spark plug wires for arcs by looking under the hood with engine running after dark.

(5) Find out what the stock tailpipe diameter was. It appears that the muffler shop that put a muffler and tailpipe on it a couple years ago downsized the tailpipe 1 or 2 sizes. The tailpipe appears to be 2" OD, and is definitely smaller than the pipe on the engine side of the muffler.

(6) Investigate if the mpg chips on the market are cost effective (or if they even work).

(7) Keep pressure in tires between the psi on the tag at the door and the max. psi listed on tires.

(8) Oh yeah, make sure T stat is working properly, so that the engine warms up quickly.

Did I miss anything?

Thanks,

Mac_

Mac_

The pipe between the cat conv and the muffler is 2-1/4" OD, vs a 2" OD tailpipe. The tailpipe reduces the cross sectional area about 25%' si I've got to believe this has to be part of the problem.

Mac_