A car with a malfunctioning or faulty PCV valve may run poorly. The motor may be noisy, and the car may not accelerate as quickly. A vehicle with a defective PCV valve may also experience a loss of power. A bad PCV valve will not prevent the engine from running, but it may cause the motor to overheat. A car with a damaged PCV valve may also have a leaky exhaust system. Leaking exhaust can cause the vehicle to emit an odor.