Ben,
The condition you are referring to is called "Icing". It is caused by the
expansion of the air that goes around the throttle plate at idle and road
load conditions. It generally occurs when the ambient air temperature is
slightly above freezing and humid. As the air expands beneath the throttle
plate, it cools to below freezing and cannot hold as much moisture as it can
above freezing. It deposits the excess moisture around the idle ports as ice
and shuts off the fuel flow. It is apparent after the fast idle cam is off
and persists until the engine is fully warm.
The test for this condition is that when the engine dies at idle, DO NOT
touch the accelerator. Wait 30 seconds or so, and restart the engine WITHOUT
touching the accelerator. If it then idles normally, it is because the ice
has melted.
The fix is HEAT. The manifold heat control must be operating properly or all
hope is lost. The manifold heat control was always a problem due to carbon
buildup from the exhaust, even on fairly new vehicles. After 30 yeqrs or so,
there is a good chance yours is frozen in the open position.
If you can spray a corbon solvent on the shaft and gradually work it until it
frees up, your problem should go away. BE CAREFUL about how hard you twist
the counterweight, because it is not keyed in place and frequently twists
around the shaft before the shaft is free. DO NOT use oil because it can
cook on the shaft and make the problem come back sooner than it should.
After it is freed up, occasionally (While the engine is cold!) reach under
there and flop the weight back and forth to keep it free.
Hope this helps... Good luck!
Joe Savard
Lake Orion, Mi
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