For some reason my truck idles high. Gotta 88 f150 with the 302. The shop fixed my timing, at least thats what they told me. But when braking the rpms would drop down how it pose to, then go to like 1500 then back down then back up again. it idles in park like at 1500. im stuck. even when coasting it stays in a certain rpm. i was leaning toward a transmission problem. I need answers please.