I have a similar problem. '02,,3.0, 141000 miles,

Starts right up after its been sitting overnight. after its warmed up when you go to start it up. It churns but doesn't start. I never let the starter to just keep running for more than a couple of seconds. It always starts on the second try.

OP, how do you know only a few cylinders are running at first? I don't notice anything like that. Did you put it on some kind of test computer or the like?

I was wondering if maybe it could be a bad injector. the spark plugs have about 50,000 miles on them, I'm told they go 100K. Any thoughts.