The TCV renders the LST inactive if the vehicle is operated with a cold engine (coolant temperature below 6C (14F)) or at high altitudes (where the atmospheric pressure is below 93 kPa (70mmHg)). The purpose of providing a TCV is to prevent misfiring. If the injection timing is allowed to keep advancing at conditions where misfiring occurs easily (cold engine or high altitude), misfiring is prevented. Then, white smoke is also prevented. The emission control ECU determines the conditions of the engine using signals from the water temperature sensor and the atmospheric pressure sensor.
Then, the emission control ECU outputs signals that cause the TCV to close the fuel passage of the LST, thus rendering the LST inactive. TCV on Before the engine has warmed up (coolant temperature below 6C (14F)) or when the vehicle is driven at high altitudes (where the atmospheric pressure is below 93 kPa (700mmHg)), the emission control ECU outputs signals that cause the TCV to turn on and close the fuel passage. Therefore, even if the accelerator pedal is released and the engine load decreases, the LST becomes inactivated and does not retard the injection timing.