Jim:

Yesterday afternoon, I had yet another tech measure my idle speed with a hand-held computer; he showed me the readout, which was nearly 800 RPM.

Suspension of disbelief aside, I must (by the law of averages) assume my idle speed is above 600 RPM.

Perhaps I have been barking up the wrong tree: now, I believe my problem to be related to my throttle body (fuel/air micture = too lean versus too rich).

Sincerely,