i was wondering how you figure out what the check engine light is complaining about. over the last couple of weeks i have noticed the check engine light come on but about as quick as i notice it come on it seemed to go off.

 

scan for codes.

 

https://www.f150forum.com/showthread...ewpost&t=10907 . This sticky will show you how to check codes. You'll need a haynes manual to decode the numbers . Even when yr check engine light only flashes for a second the computer stores a code as to why it flashed so you can
check later.

 

i checked the codes and not really helping much. the only codes i can find i think were caused by me play with my scan tool 522 179 211 556

 

Those are some pretty serious codes. 522 is no real problem. It says you didn't have the vehicle in park during testing. 179 says the system is rich at part throttle. 211 say the pip signal was missing or erratic, meaning there was no spark control. That probably caused the rich reading. 556 says you had a fuel pump relay fault. I would clear the codes first then drive for a full cycle, stop, go, cruise, idle, highway speed and full engine temp then retest. What year and motor do you have.

 

95 4.9 with 5 speed. i guess i will clear the codes and check again. i just don't know how these things work. i figure if the check engine light came on it was suppose to stay on until things were fixed or the codes were cleared.

 

well i just took it out for a cruise i get 111 and 179. now that i think about it the truck has been getting worse and worse gas mileage over the last couple of weeks. i have burnt about 3/4 of a tank of gas and only gone a bit less than 250km's.

 

The codes are triggered by various conditions in the engine ( rich lean speed timing etc ). Usually the computer must see the condition twice to set a code. If it doesn't happen again after a certain number of run cycles it will clear. Some codes are stored but don't activate the light. Some codes activate other codes so if you have multiples it is good to clear them and retest the system.
111 is system OK. 179 is reoccuring so we should look at that. At partial throttle only the O2 sensor is reading rich. Remember these are old style O2 sensors they only read oxygen not fuel. So what it is saying is when you are at part throttle the sensor is not seeing as much air as it should. Places to check are your TPS sensor , maybe the throttle isn't where the computer thinks it is. The IAC may be restricting air. The throttle plate may be sticking. The MAF or map system may be reading wrong as they help determine air intake. Or the O2 sensor or its wiring may be bad. An exhaust leak can also cause this reading by letting oxygen out before the sensor. Stuck valves or bad cam or timing could also cause a rich reading. A vacuum test on the engine and a timing check can help eliminate some of these issues.