idle after shut off

[mccomas]

every once in awhile (1 time out of 10) when i turn my rig off, it continues to idle (not a real idle but you know what i mean) for a few seconds, is this some type of detonation or continued fuel flow and what can be done about it.

 

[slider]

Your idle spped is probley too high. If it is too high the carb idle circuit will not work correctly, the throttle plates should be closed so the idle circuit can work. If the throttle plates are open at idle you get run on after the ignition is shut off.

 

[rjfguitar]

It is dieseling, check how high your idle is and most importantly check your timing. To advanced or retarded timing will cause it to diesel down. If it is a small block than I would set the timing at about 10 degrees advance at idle.

 

[R72K5]

it is dieseling yes and can damage your engine if you dont correct it ASAP

too far advanced timing or too fast of idle speed are causes, also overheating is a cause too

good luck

 

[Blazer1970]

If it only does it intermittantly, check to make sure your throttle plates are closing all the way all the time. Try tapping the gas pedal with your foot and letting it pop back up while it is dieseling.

 

[elacruze]

'86 is still carbureted, right? You have an idle solenoid, which holds open your throttles to running idle speed, but allows the throttle plates to close 100% when you shut off the key (powering down the idle solenoid) If this solenoid sticks, it will allow the engine to pull fuel and run on after shutdown. This will happen on late carbureted motors even when nothing else is wrong-you don't have to have overheating or timing problems. It's the nature of the beasts, that's why GM put the idle solenoid there in the first place; to cure the dieseling problem. Clean it, lube it, if it still happens, see if you can verify the sticking solenoid and replace it.

Eric