IAC fried?

[ChevyTech]

Many TBI trucks get a strange rhythmic misfire or stumble at idle when the fuel has ethanol in it. The higher the ethanol content, the more noticeable it is.

I you have poured anything in the gas tank, wait until you have a fresh tank of fuel before you get to involved in the idle misfire.

If the system is retarding the timing just before the misfire happens, I would watch the knock counts and see if there is a considerable increase just before it retards the timing. If so, I can go into detail on the possible causes.

If the timing retards happens just as, or just after the misfire, I would say the misfire caused it.