I have a 98 Windstar 3.0 with 128k miles on it, and over the past few months it has had a problem with hesitation and bucking. The problem is intermittent.
My mechanic has diagnosed a few things so far and a lot of money has been spent on 'repairs' but nothing he suggests fixes the problem. I've now taken it back from my mechanic and his "shotgunning" repair technique in order to try and diagnose the problem myself.
So far I've replaced the Throttle Position Sensor and the Camshaft Position Sensor, and while that seemed to fix it for a day or two, the problem came back. (It's intermittent nature means it can run fine for days).
There seems to be no rhyme or reason to the hesitation, it can happen when you're pulling away gently, or when you're cruising at highway speeds, or during a shift, pretty much any time. Turning overdrive off, or keeping the transmission in 1st or 2nd makes no difference. Also you can drive it really hard sometimes without the problem manifesting at all. Often I'll drive it hard 10 miles to work and it's fine, then it will act up on the way home with about 3 miles to go.
As good as I can tell it feels like the engine is cutting power to the injectors or plugs all at the same time. And the loss of power can last from a fraction of a second to a whole second before it recovers. Sometimes you just feel a bit of spluttering as though only a single injector or plug isn't firing. I thought it might be a transmission problem, but I'd imagine that the revs would climb while the transmission slips, and that's not happening.
I've also had poor idling on occasion, but it's very uncommon, so may not be related.
Any ideas what to try next?