When engine RPM starts jumping around, the cause can range from a simple air-intake issue to a deeper problem in the fuel, ignition, or engine-control system. In most cases, unstable RPM points to ...
View post: Amazon Has a Craftsman Impact Driver on Sale for Just $52 You notice it every time you get in the car — when you start the engine, the gauge called a tachometer tells you the RPMs. But, ...