03 4.2 help!

[KennyJoe55]

My 03 F-150 2wd, 4.2 has thrown two codes P0171 & P0174, which made me think it was a problem with the mass air flow sensor which i replaced ($100.00) but after a short time the check engine is back on with the same codes! I've replaced the mass air flow sensor under warrenty 2 more times! It's on it's 3rd mass air flow sensor in a month, so that's not it! It's also now showing a pending code of P1131 (misfire on bank 1). The truck seems to run and drive fine but the light is driving me crazy! Sometimes the idle is up and down. Second problem is there is a vibration at idle speeds. I can make it go away by raising the engine speed. Torque convertor shudder maybe? The truck has 170,000 on it. Can anyone help me figure this out? Thanks, Kenny.

 

[kevin9]

You most likely have a vacuum leak. Look very carefully at all the rubber hoses and vacuum connections. It is also possible that the intake plenum gaskets are leaking,but the most common complaint with those is rough running cold then gets better as it warms up. The 1131 code is not for a misfire but for insufficient switching on bank one. This is not a bad oxygen sensor, it is the computers way of telling you that bank one is staying lean. I am a professional mechanic,so if you need more help let me know. My e mail is [email protected]. Good luck! Kevin