06 F150 5.4 Missing?
Hey guys, I'm looking for some guidance! I have an 06 F150 FX4 CC w/ the 5.4. I bought the truck used about 2.5 yrs ago w/ 70K miles on it. It now has just over 96K miles on it. I've never had an issue w/ the truck until two days ago.
The trucks seems to run fine except for when it shifts into O/D and only if I'm feathering (gradually increasing) the accelerator. At this point, the truck starts vibrating and engine fluttering badly (usually around 45 mph). If I gun it at this point, everything seems to line back out and run smooth again. The truck has an Edge programer that was already installed from the previous owner (almost didn't buy the truck because of this). Those things make me nervous! I don't drive the truck on anything but the stock setting. I just keep the programer hooked up to monitor different parameters and it looks kinda cool at night.
At first, I thought it was a transmission issue developing. Well, I was playing w/ the parameters on the way home from work this evening and noticed a few things. When the truck is acting up, the FRP (Fuel Rail Pressure?) and LP (Line Pressure?) remain constant whether truck is acting up or not. However, when it starts acting up the Spark Advance drops from 36-34 down to 4- -2. As soon as I let off the throttle or gun it, everything returns to normal. If I disengage the O/D, it seems to run fine. I'm leaning towards an ignition problem or spark plug issue now but I really have no idea?
Has anyone else experienced these symptoms? Any help or guidance I can get would be greatly appreciated!