I have a 1989 ford econoline 350 with the 460 (7.5) motor has 102,000km when it's running from cold start its great once you start driving bit distance it sticks open sometimes you can hit accelerator hard it comes down but last run on hwy 400 it stuck wide open almost ran into a school bus I've had it to several mechanics whom have sprayed heck out throttle body, one put extra springs on it ,another disconnected the cruise control saying its the problem ...it still does it I keep trying to tell them it's probably the throttle body itself nobody listens any suggestions would be great it's in a motorhome.

 

I would suggest checking the throttle linkage starting at the throttle body, disconnect the cable then verify it is not binding inside the vehicle.

 

Thanks for the input I give it a go an let you know.