[Konham]

Ok this is messed up. I drive conservatively and I never get above 9 mpg. I have a 5.8 with EFI. I put in new spark plugs gapped to .055 with the msd coil. Also 9mm wires, msd rotor/cap. K&N cone. Stock exhaust. I have 31" mud tires and stock gears (3.55). E4OD, replaced all fluids (trans, diff, tc, etc)This is killing me slowly, NEED HELP/ADVICE!!!

Thanks.

 

[Konham]

sorry for double post, interent lagged out

 

[topfisherman]

Check for dragging brakes, or possibly a plugged cat. Has your O2 sensor ever been replaced?

 

[RLKBOB]

I agree also pull codes and see if you have any stored(even if you don't have a CEL). How about fuel filter, ever been replaced? Does your OD work on your trans and do you use it? How many miles?

 

[TheUnforgiven]

is the exhaust crimped badly in any place?

 

[884lps]

Take it to a muffler shop you trust. They should charge no more then about 20 or 25 bucks to check your back preshure. If it checks OK its not the cats, muffler or pipes..

 

[MyFullSize]

Your only a little worse than when it was new....

http://www.fueleconomy.gov/feg/noframes/10559.shtml

My '89 did about 12 with a fresh 351, but after a year, I only got 10, never better... never worse.

 

[Switch]

I put in new spark plugs gapped to .055 with the msd coil. Also 9mm wires, msd rotor/cap.

I thought stock gap was .044?

James

 

[RLKBOB]

With an MSD coil you can open it up to .055 to get a bigger spark and better performance and mileage(theoretically).

 

[Switch]

Oh... I learned something new. :thumbup

James

 

[bronco23]

dude, electric fan, youll definetly notice increase

 

[MyFullSize]

dude, electric fan, youll definetly notice increase

Yup, from 9.5 MPG to 9.7 MPG! opc1:

 

[Switch]

I can't wait to see how my new motor does with the ZF tranny.

James