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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
...You would be sucking in un-metered air anytime vacuum was present, and leaking out pressurized air when on boost. Bad scenarios, both...
If there is a brake in one of the tubes or the can to atmosphere that could be a vacuum leak of unmetered air with the typical effect?

If the internal spring or the diaphragm fail, I am thinking the deaccel valve would just effectively pass air around the throttle plate with no effect on metering but it would effect idle quality.

The effect might be unstable idle, lazy return to idle, and or no of the intended de-accel valve function.

The thermo time valve closes the Vac-Retard line to the pot on the distributor which has the effect of advancing timing and speeding up idle speed.

If it fails open, idle would be low on start up. If it fails closed idle would be elevated when hot. If it fails creating a restriction it might slow the return to idle.

Disabling the thermo valve should make for a lower idle speed when cold.

It would seem that either or both of these could have created the issue Dave described.
Old 10-01-2010, 07:53 AM
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