Howdy,
I have a 95 4 liter 2wd Aerostar, 126,000 mi. that runs ok until warmed up. After it's warmed it starts to miss and buck at higher speeds and just idle badly at a stop. This happens under accelleration or steady throttle. No noticeable smoke when this occurs.
Recently I have replaced the MAF, the fluid temp sensor, the air temp sensor, the throttle position sensor, (all after trouble began) the oxygen sensor and IAC a couple months earlier, plugs and wires about 15,000 miles back.
Any ideas?

I had the same issues with my Windstar. Although they cost about $50.00, change the EGR valve. At 126,000 miles, they tend to gunk up and then the engine idles poorly, cuts out at stop signs etc.

Good Luck!