There are many components in a vehicle that are so small that they go unnoticed. One particular part that is small, but also has the potential to damage a vehicle's fuel economy, is a knock sensor. When the check engine light is on, there are loud pounding noises coming from the engine, or a driver has trouble accelerating, the cause of these issues could be a malfunctioning knock sensor. If looking for a replacement knock sensor, one place that drivers can turn to is PartsGeek.com. In fact, Parts Geek is now offering over 6,000 knock sensor parts.