I am getting 3 codes: P003, P0171 & P0174. The engine just started running very rough. Check engine light is on. it is a 1999 ford f150 4x4 5.4L 120000 mi. Is this something that would come on suddenly? Truck was running fine and I stopped to get gas and it started running rough on restart after fill up
Answer:
This is a great example of a vacuum leak. More than likely the intake gaskets are shot and need to be replaced as this is the most common issue with the fords and these codes.
It is possible to happen all at once, it is possible that you just got some bad gas then. I would put some octane boost in it and run the gas out then fill it with good gas from another station. If that doesn't clear it up, then you will need to replace the intake gasket or repair the vacuum leak. by spraying brake wash around the top of the engine(not on exhaust) while the engine is running and listen for the engine to change to stumble.
