First off its a 2006 F150 king ranch with the intercooled roush kit and roush tune. Last couple weeks its progressed from a slight stumble on start up, to now after its been off for a few hours it may start and run rough for a second, or, it may start then die, and then have to crank for at least 5 seconds before it starts. After it starts it seems to run fine.I've thrown the P0172 and P0175 code a few times. I downloaded the torque android app and did some data logging. Can you learn anything from the long term fuel trim? Any help is appreciated.

 

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If my LTFT stays in the negatives is that bad? And what does it mean? It ranges anywhere from -15% to -30%, never going positive on either bank.

 

It sounds like the fuel pump is on its way out and leaning out the motor. 15-30% below the needed fuel is not good

 

If I'm not mistaken, the negative LTFT means that the computer is cutting that much fuel because it has detected a rich condition, hence the P0172 and P0175 codes. Am I correct?

 

Thanks guys....I really appreciate all the help (sarcasm). I fixed it anyways.

 

so what did you do to fix this problem?

clearly we couldn't help, so why not post up the repair to help the next guy in your predicamint.

 

You would never guess, or at least I didnt. Went to start the truck after work and the battery was dead,the temperature was in the teens to low 20's all day, and the battery looks like the original from 2006 so I jumped it and went and got a new battery. I think that was my problem, fired up quicker than it has since ive owned it and the LTFT's were back to 0 on bath banks. It even seems to run a little stronger. I dont know it the old battery was just to weak to completely burn, the fuel with the supercharger and colder plugs or what.

 

These trucks get strange symptoms when the voltage gets low or inconsistent.

 

What's painfully obvious to some, is unseen by others.

Very well stated, Dano.

Stewart