I have a 1997 f-150 with 91000 miles on it. It has the 4.6 engine with auto trans. I have changed the plugs and air filter. the fuel mileage is terrible. It went from 17-18 on the hwy to 10-12 miles. no check engine light or nothing, motor runs fine with no miss. Wouldn't be that big of a deal to me, if the price of gas wasn't 1.65 to 1.85. any help would be great.


Thanks,

Rodney

 

You may want to replace the upstream o2 sensors. Still have to do mine, did everything else but still have crappy mileage.

 

Here's some of the things I have tried;

Clean MAF sensor with electric part cleaner
Clean carbon out of throttle body
Run 1/2 can of Sea-Foam through the throttle body
Clean fuel injectors using the other 1/2 can of Sea Foam
Change the DPFE sensor
Change PVC valve
Change fuel filter
Change the front (2)O2 sensors

The MAF, Sea Foam, DPFE and O2 sensors gave me the best results.

I have a strong suspicion that my gas mileage will never get above 12 - 14 mpg because of the increase rolling resistance after I upgraded from a 4 ply passenger tire to a 6 ply truck tire.

Good luck and let me know if anything works well for you.

aloha,

Ihilani

 

Sounds like your engine is staying in open loop. This can be caused by an incorreect or faulty thermostat or engine coolant temp. sensor.

 

I wouldn't think that going from 4 ply to 6 ply would decrease your mileage. It's always been my understanding that more plies roll easier, not harder. May be due to the tread pattern/characteristics.