jeremy j

My truck has 162 xxx kms on it, plugs were changed at 100 and where burning good. My gas mileage went from 20+ mpg to around 11 mpg. I really noticed a difference in the last 6 months or so. I pulled all the plugs a few weeks ago and all are burning really lean. Replaced all the plugs, new fuel filter, cleaned the K&N air filter and cleaned the maf sensor and no difference. It is not throwing any codes either??

torkum

What kind of plugs did you put in?

jeremy j

Motorcraft both times i changed them

torkum

At this point I would need to see the LTFT from a scanner reading. Maybe a O2 sensor problem but I wouldn't go throwing parts at it without some testing.

jeremy j

Had the truck at the Ford dealer over the Christmas holidays and they couldn't find anything and had it to another shop today not sure what the readings where but he said the readings on the o2 sensors where perfect. What should the fuel pressure be at idle?

torkum

Fuel pressure should be around 40psi +/-. What all did they check?

jeremy j

I know they checked the o2 sensors and the coolant temp sensor, not sure what else, I just checked the fuel pressure and its only holding 30 psi at idle and around 38 when you give it some fuel.

racin4ds

iTrader: (1)

Sounds like your Fuel pressure is low, If I'm not mistaking it should be 39psi and over 42psi with vacumn off. Might be your pump. Also if your 02 sensors are original with that many miles, I'd replace them anyway, cheap insurance and peace of mind.