85 K100 ...all of a sudden backfiring and stalling when HOT!

[Atabeach]

Ok was running absolutely perfect, yesterday...she always backfired under deceleration but now on low rpm throttle. Starts right up, soon as the temps get op backfiring & stalling on low RPM.  OK soooo I used the propane trick to check for leaks at the throttle bodies...no noticeable increase in RPM. Pressed the starter button, verrrry slight decrease in RPM. The fuel pump is new , Z hose new...checked for leaks in and around air box... next Im going to take out plugs and see how they look. any usual suspects Im missing? TIA
 

[Laitch]

Verify that the battery positive clamp, the battery ground clamp and the battery ground cable attachment on the transmission are tight.

Click this link to the opening post of the Service Manual section here. Click on the link to Vogel's troubleshooting guide at the bottom of the opening post. Perform the tests of the throttle switch and the coolant temperature sensor explained on pp. 21–22. Let us know the results.