All winter truck runs great. Soon as the hot weather arrives [ the hotter the more frequent ], the truck will hold at a steady high idle sometimes cruising at 35 mph or above as if I had cruise control [I don't ]. No check engine light, iac changed twice. Each time it was changed it seemed fine for about 2 weeks. Pvc valve chanced and some vacuum hoses also. Want to be ready for this summer. Any suggestions?