Hey,

I've got a 2000 F150 with the 4.2L V6 with roughly 358,000KM. When driving highway speeds around let's say 90KM/H and your just giving it enough pedal to maintain speed and coast, and then you give it a little tiny more on the pedal enough to maintain speed going up a hill lets say or go by a car turning off to the right, well it has a quick sudden like clunk or knock to it.

The symptoms are similar to when my mass air flow sensor went, but it only does it around that speed and when you try to go from coasting to accelerating slightly - If you hammer on it, it doesn't usually do it. The clunk or knock is sometimes worse when its a cold day and you've driven for a bit.

Kinda scares me... Doesn't seem like a transmission or engine problem. Any chance it could be the spark plugs and wires? I was thinking about changing them anyway but I don't have too much extra money to dish out until I need too but I wouldn't mind resolving this problem.

Thanks for your input,
Brendan