I recently bought a 91 f-150 with a efi 5.8 with california emissions. I have replaced the fuel filter, plugs, wires, cap, rotor, and o2 sensor so far. I am getting a check engine light when i drive it. It will go out and come back on while driving, and will not come on in idling. and if you turn the key off it clears the light. the exhaust smells really rich and the fuel mileage is terrible. i can't get the check engine light to stay on to scan it so does anyone on here have any ideas. also when starting cold it stumbles a little bit but then will run fine. if you need anymore info let me know and i will see what i can do for you. thanks for any and all info.

 

was check engine light on before you replaced the sensors, if so you may need to clear
the codes. then run the truck to see if the codes return.

 

im new at this how do can ya clear the codes with out a machine

 

light was on before i changed the fuel filter and it went away for two or three weeks. came back again. so i changed the fuel filter again since both pumps are whining like they were before. now light is on again.

 

i usually clear mine by disconnecting one of the battery cables.

 

gotcha .. i was thinking that there was a nother way

 

ok after letting the truck sit for about two days i went out to start it and i had to pump the gas while turning over the engine to get it started. it is about 70 here today so it should have started right up. any ideas? I bought a code scanner from ebay. i am hopin that will give me something that i can pinpoint the problem too. thanks.

 

you don't have to buy a scanner. Go to fordfuelinjection.com and you'll learn all you need to know about codes. And you can clear codes by disconnecting the ground into the plug while running the code test. That or disconnecting the battery for a while.

 

qman is correct. you should check your fuel pressure. fuel pumps r not supposed to whine they r supposed to buzz. if u have injectors you should not have to pump your gas pedal

 

I replaced the fuel pressure regulator friday and that seems to have fixed it. I can't smell a really rich exhaust anymore and i drove 80 miles to work today without getting a check engine light. and my mileage has improved. looking in the old fpr i think dirt got in it and stuck it open. i didn't check the actual pressure but the pumps stopped whining and all seems well. KNOCK ON WOOD!!!!!!!!

 

thank you for the info but i have a bad pump also