I own a 1999 F-150 X-CAB 4x4, 5.4 liter V8. In the past 2 weeks, when I start the truck, on two occasions so far, the truck won't stay running unless I leave my foot on the gas. This goes on for awhile after I drive as well, I have to keep giving it a slight bit of gas to keep it running when i am stopped. After a few miles, the truck begins to run fine again. The only recent modifications that were made were the addition of an Excalibrator Multi Program OBD II Flash Device. Any ideas if this might be programmed wrong and causing the problem, or is it something else. if so, what?

 

Try cleaning or replacing your Idle Air Control Valve (IAC). Looks like a roll of quarters attached to the throttle body.

 

When was the last fuel filter change? Is it doing this on the same tank of fuel? Maybe bad fuel?

 

I posted this information on two other forum sites and these are the exact same responses that I got there as well, so I at least know that is where to focus the attention. It has been on the same tank of gas come to think of it. The fuel filter hasn't been changed for quite some time so I think between that and the IAC, if I replace them both, I should correct the problem.
Thanks again.