Well, my bone-stock '86 240 (B230F) has been idling high lately. It's also been pinging at higher rpm; particularly on the freeway, but also around town when not even under load. I've cleaned the throttle body (the usual idle culprit) but still cannot get the base idle below 1000 rpm.

Due purely to suspicion, I removed the upper timing cover. The mark on the belt is one tooth behind the mark on the sprocket! That could easily be causing both of my problems, couldn't it?

Seems to me that although the belt is reasonably young, I ought to get it changed--and then re-tensioned at 600 miles. Am I right? Or is there a shade-tree solution for the time being? I sure don't want to release the tension and/or rotate anything unless it's safe to do so.

The excellent help here is always appreciated...thanks!