A spark plug tester will help you quickly diagnose a breakdown in your car. If you have unstable idling, stalling during acceleration, or "pops" from the exhaust pipe, the problem may lie in damaged spark plugs. To check them, wait until the engine cools down, then unscrew the spark plugs and screw them into the tester. Next, the tester is connected to the electrical network and by turning the knob a breakdown test is performed. The compact device will not take up much space in your garage and will help you quickly determine the cause of unstable car operation.