I purchased a 07 with the 5.4L 3 weeks ago. During the first few days after driving it around 20 miles the engine would shudder, make a knocking sound and act like it wanted to stall out when I came to a stop sign. This happened on 4 occasions. All the gages read as normal. I replaced the fuel filter, added some lucas injector cleaner and filled it up with premium as it had been running on fuel from a fleet service vehicle thinking they might be putting in cheap gas. It quit doing it until Sunday a week ago when I was backing in after a long drive on the highway. I subsequently took it to the local garage who put it on the computer. He said no codes came back and he couldn't replicate the problem by cruising around town. Its been fine until tonight when it did it again as I was backing in the driveway.

I am stumped.

 

Torque converter clutch is not disengaging the t/c and causing the symptoms you feel. Focus on trans, not engine.