Engine cylinders must be sealed to prevent blow-by and oil loss. PCV valve filters oil mist and particles to allow only gasses in. Valve stays closed under idle due to engine vacuum. Valve opens fully at higher RPM to reduce emissions
MAF is located between air filter and intake manifold in modern cars. Measures air entering engine and uses hot-wire type with temperature sensor. Translates electric current into digital signal for engine computer. Controls fuel injection and automatic transmission shifting
Sensor measures camshaft rotation and sends data to engine control module. Located near front or top of engine, sometimes behind timing cover. Determines which cylinder is in power stroke relative to crankshaft