What Happens When Your Distributor Cap Goes Bad?

by Keith Evans
David Broberg/iStock/Getty Images

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.


Misses in the engine can lead to a rough idle.

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

A bad distributor cap may also have physical cracks.

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 newer cars don't have distributors.

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.