A vacuum leak is a leak anywhere between the engine and a mass air flow sensor. In most cars, a mass airflow sensor is installed at the air filter box. In the fuel injection system, the mass air flow sensor measures the air flow into the engine. The engine computer (Power Control Module) calculates how much fuel to inject based on the mass air flow sensor measurements. If there is a vacuum leak anywhere between the engine and the mass air flow sensor, it causes "unmetered" air to enter the system. This causes the actual air flow to be higher than the mass air flow sensor measures. As a result, the PCM miscalculates the amount of the injected fuel, and the engine runs "lean". The term "lean" means too much air and too little fuel. The effect of a vacuum leak is more noticeable at idle, when the air flow is lower. Air induction system schematic Vacuum Leak Symptoms Symptoms of a vacuum leak include the Check Engine light, rough idle, stalling and a hissin
By Voiture Verte Autocare Services