After long trips over 100 miles or more the engine makes a surging kind of noise (when in park) and goes between this constant noise and then smoothes out to almost normal idle. At times when I'm on the road (over 100 miles on a long trip) and I hit the gas nothing happens till about 5 to 10 seconds later. The engine doesn't rev and the tranny doesn't shift until 5 to 10 seconds later and then of course the van rev's high because I've floored it and starts to function normally again. I can pulse the accelerator and usually on the 3rd or 4th pulse of the foot is when it kicks in. I've had the tranny rebuilt recently. It is almost as if the engine isn't getting gas properly. Any ideas? I have 140k on my Windstar. It has begun to operate erradically now during normal in-town driving only after a couple miles almost acting like it will kill at times, but then it catches itself and resumes operation.

I would check a few things. First pull a spark plug and see how there burning rich or lean. Next Check for a vacume leak. One problem on the 3.8 litre engines is the pre molded 90 on top of the intake manifold it becomes cracked or so soft the vacume actually collapses it. Check the IMRC vacume lines the two valves connected to the manifold on the passenger side. These should open at about 2500 rpm. With the van in park and emergency brake on work the throttle from under the hood and see if these move. If not check for a vacume leak related to these lines. Im assuming your getting no CEL (check engine light.) If you have a vacume gauge you could use it to check and see vacume pressure at that same port at the top of the manifold. The gauge should be steady and when acceleration icreases the needle should move smoothley and back again when the accelerator is released. Possible fuel pump problem or fuel filter. Check plugs first. Post back with findings or codes.