well the truck is an 1994 4x4 automatic 5.8, The check engine light came on and i scanned it and it read a code 173. Which means running rich. I replaced the o2 sensor and still the same
code even after i cleared the computer . I new the o2 sensor was a long shot but i tried, it was only $43.00. The truck has 112,400 miles on it and runs great, just of course she is sucking the gas.
What should control the running rich or lean in the engine? a sensor, egr valve etc... I need help anybody a.s.a.p. as she is killing me on gas mileage 11 or 12 is all i am getting right now and
that is on the highway.

HEEELP!

 

The first thing you need to do is check the fuel pressure. Check it with:
1) the key on, engine off
2) at idle
3) at idle with the vacuum hose to the regulator disconnected and plugged
4) the key turned off, to see how quickly the gauge bleeds down.

Post your results.

 

right side o2 sensor running rich. see www.fordfuelinjection.com for codes. Get a Haynes book and test each sensor it could be some of them. Check the vacuum plastic lines that run under the upper (intake manafold) these melt. Just fixed mine on 87 f150 Clean out your Tps sensor on your throttle body with throtte body cleaner only, watch out for the sensor. If your fuel pressure is high change your oil to. Let us know what your fuel pressure is first? Fuel pressure should be 35 to 45 psi engine off, running its should be 30 to 45psi press down throttle should be about 45 psi.