Aerostar Cruise Control

just bought a '95 aerostar w/ 94,000 miles on it. The cruise control surges slightly when set above around 55 mph. Nothing big, it seems to hold speed fine, but is on/off throttle pretty often and less gradual than other vehicles I have driven. I have an '82 E-250, a '94 Civic and a '90 Aerostar that all operate more smoothly than this one.

I changed the cap & rotor, plugs & wires, and the air filter. I also cleaned the throttle body and mass flow sensor and disconnected the negative battery cable overnight to clear the CPU. all this led to a slight improvement but the problem is still there.

I used a code scanner and no problem codes came up.

Any ideas?

The '93 did that in the mountains, especially when you had to shift from overdrive to drive just to maintain speed up and down hills. I have no idea other than I learned to deal with it and then sold it to someone else and had it become their problem :evillol: