Engine misses while mantaining speed

I have a 1996 ford windtstar with a 3.8l angine and 130000 miles. I had my codes read at a dealer and they changed my dpee sensor, and told me I may need a coil and wires, I replaced both and car does same thing. My car is missing while mantaining speed, and the check engine lite flashes. When I accelerate it comes out of it in 5 to 10 seconds only to do it again soon as I mantain speed again. It also does it more once the outside temperature is above 32 degrees, and doesn't do it at all when the temp drops below 10 degrees. Thanks chris