This problem started last summer - with A/C on car ran fine until engine got real warm (heatsoaked?). After that, when coming to a stop or idle engine would suddenly drop in RPM and rumble/stumble, then die. It could be restarted, but would stay in the stumble condition, and would not respond to gas pedal. If left to cool for 30-45 minutes, engine would restart and run, until it got hot.
Since the original problem (never throws a code, except sometimes a misfire code when engine is stumbling) I have replaced plugs and wires, the ECM, IdleAirControl, and the latest is the IgnitionControlModule - all expensive "guesses" on the part of experienced (?) and well-meaning "shade-tree" mechanics (including me) - but the problem still occurs
.
I have also tested the coils (cold) and all were the same, about 5% below the spec (included with the new ICM).
Lately, the problem can show up even when the sun is shining on the hood, last time on a sunny, 70 degree day, from a cold start. Obviously, whatever is the problem is getting worse.
I've had suggestions from "sugar in the gas tank" (problem ought to show up all the time, right?) to "bad grounds" (checked every one I can find, all connections were cleaned/replaced), but I still haven't found the Magic Bullet.
Jeffcoslacker, got any extra bullets?
