... at least I'm pretty sure. When rolling along and the throttle is released immediately rather than gradually, if my idle speed is too low, the engine is silent and takes a moment to kick back in. (That's the best way I can think of to describe it). I had been toying with the idle speed screw, which is why I believe it is related, but was wondering if there is another cause. Could this be referred to as the engine "missing"? When I raised the idle speed, it ceased occurring.