The intake boot provides a pathway for air from the air flow sensor to the intake manifold. On most BMWs the boot is made of rubber with an accordian shape that allows the engine to shift and vibrate. As with any rubber component the rubber can dry out and crack and that can lead to serious running and drivability issues. A crack in the boot means that air is entering the engine that is not being monitored by the airflow sensor. The engine computer relies on data from the airflow sensor to set the fuel mixture in the engine. Excess unmetered air can result in lean condition faults, rough running, misfires, and other performance issues. For misfire and lean condition faults, check your intake boots first.
As an alternative to the original rubber, we also offer silicone boots that are both stronger and last longer with a 4-layer silicone design. Samco silicone boots can also decrease your BMW's intake turbulence and restriction by replacing the accordian design with a smoothed internal surface. Samco boots are also perfect as part of a kit to eliminate the factory traction control system (sometimes called an ASC delete boot).
