What Happens When Your Distributor Cap Goes Bad?

Written by keith evans Google
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What Happens When Your Distributor Cap Goes Bad?
Distributor caps control the flow of electricity to an engine's spark plugs. (car engine image by itsallgood from Fotolia.com)

The distributor cap, the top part of a car's distributor that regulates the engine's firing order, serves as an integral part of an automotive ignition system. When the distributor begins to fail, drivers may notice symptoms that range from a rough idle to a car that will not start.


According to the automotive website Clark's Garage, a cracked distributor cap can cause a car's engine to miss. Misses in the engine may lead to a rough idle and hesitation during acceleration. A completely failed distributor cap will also interrupt the flow of electricity to the car's spark plugs, preventing the vehicle from starting.

Signs of Wear

In some cases, a bad distributor cap may display physical cracks. Clark's Garage notes that distributor caps do not always display physical symptoms, so vehicle owners may need to remove the cap for testing.


Many new cars, according to the automotive website EconoFix, do not have distributors. Because distributors and distributor caps are somewhat prone to failure, many newer vehicles now include distributorless systems known as direct ignition, or DI, systems.

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