When a car's distributor cap becomes faulty, the sequence of the functions of the engine will become out of order and will begin to fail. This can cause the car to have higher revolutions per minute, shake while idling, produce a high-pitched squealing noise and even begin to stall or backfire. The distributor cap must be replaced to address these issues.
Cars that are started in the cold and driven immediately or cars that are kept in extremely cold temperatures are more likely to have a distributor cap become faulty. Distributor caps are made out of a plastic material, and plastic that is heated and cooled too quickly can sustain damage. The cap can crack and burst if it is started in the cold weather on a regular basis. If the distributor cap is cracked, it should be replaced before it begins to cause other engine problems.
One of the most obvious symptoms of a bad distributor cap is a shaking car. If the car is at a stop sign or a red light and is idling and it begins to shake, the distributor cap may not be causing the proper rotations within the engine.