Toyota Repair: idling after i turn the key off, air fuel mixture, combustion chambers

Question
Hi, I have a 1990 two wheel drive ,carburator pickup...
The truck will run and sound like its stalling when the key is off.  it does this once in awhile right after i turn the key to off.   I turn the key off and the truck gags and wheezes then shuts off... and sometimes it shuts off normal when i turn the key off. 2 wheel drive, 5 speed, 4 cycl.,,,1990


Answer
It may be a carburetor problem, the engine is still getting fuel after the key is turned off and it will ignite the air/fuel mixture in the combustion chamber, this may happen because the idle solenoid on the side of the carburetor is either leaking or not shutting off, remove the solenoid and check the O-ring, the solenoid should make a clicking noise when the key is turned on/off, another reason may be that the compression is too high due to carbon in the combustion chambers or that the engine is running hotter than normal, if using higher octane fuel seems to help then I would say that this is the case.