Computer control of the EVAP solenoid regulates the purge flow of evaporative emissions from the canister to the intake manifold. EVAP flow is based on calculations by the engine management system processor typically based on values related to fuel level, engine speed, coolant and intake air temperature, throttle angle, load sense and barometric pressure.
Evaporative emissions are introduced to the engine after the computer has entered closed loop operation and the engine is at operating temperature. This is also true during start up conditions. Some engine management systems introduce evaporative vapors at idle (in park or neutral) as well as when the vehicle is being driven.
Related Symptoms
The following symptoms can be caused by a faulty EVAP canister purge solenoid.