Thunderbird V6-232 3.8L (1982)
Evaporative Check Valve: Description and Operation
Fig.61 - Thermactor Idle Vent Valve
This valve, Thermactor Idle Vacuum Valve (TIV) Fig. 61, is used on some vehicles to improve hot idle. When the engine is at normal operating
temperature, the system is activated and purge air is drawn from the canister through the PCV line and into the induction system through the
carburetor spacer. The purge air flow into the carburetor is taken into consideration when the idle air fuel mixture is calibrated and set.
However, under warm start conditions the purge control valve is closed and the choke is off which creates an overly rich idle mixture condition,
resulting in poor idle. This condition continues only for a few seconds after a warm engine start because actuation of the purge control valve is
delayed by the retard delay valve and by the time required to evacuate the vacuum reservoir.
To overcome this condition, the TIV valve is used as an air bleed valve. The TIV valve bleeds air into the PCV line to lean out the idle fuel
mixture until the purge control valve opens. The same vacuum that opens the purge control valve closes the TIV valve.
