2003 ford f150 supercrew trk

I have maintained this truck as per specs by ford, have had all required maintenance done by ford. Truck has 91000 miles on it and recently the service required light has come on, and at the same time the engine has started running roughly at certain times. The engine runs similar as when you have water in you gas, but not all the time. Does anyone have any ideas about what could cause this? I am in a very tight financial time and can not afford to spend much $$$ on diagnostics. I am thankful for any ideas…

Check the ignition wires to see if any are loose. A new fuel filter may fix this trouble also. You can use a place like Autozone to have the codes in the ECU read for free. By letting us know what codes are set in the ECU it will help to pin down the trouble.

can not tell you how much i appreciate your advice, i am going to take your advice and will get back to you as soon as i have more info., Thank you again

finally got the ECU read and the result is PO306, from what I was told that means cylinder 6 misfire…service engine light went out for a few minutes, then came back on??? What do you recommend for the next step? I will check for loose ignition wire. I did get all spark plugs replaced at 80,000 miles. Thank you…

Run a bottle of fuel injector cleaner (such as, Techron) through the gas tank. If no improvement, continue to next steps. If this is a 4 cylinder engine, swap #6 spark plug wire with another.
If this is a V8, swap #6 ignition coil with another cylinder.
Drive the truck until the check engine light comes on, again. Have it scanned, again, and let us know the results.
There can be several causes. The next step could be to swap #6 fuel injector with another. Drive until check engine light comes on. Have it scanned. If the misfire code changes to the cylinder you swapped with, then, the fuel injector is defective.

Thank you for your valuable advice, which I am going to try…In the meantime, am I causing harm to the engine driving my truck before the problem is solved? Thank you!

finally got the problem solved, the boot on the #6 spark plug was deteriorated and spark was arching up side of plug, spark plug was ruined, replaced plug and boot and everything is back to normal, thx

It is nice to know that computers can actually help.