Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Distributor Rotor and Cap

distributor rotor and cap

A running engine sends an extremely large amount of electricity through the ignition coils to the rotor, which turns inside the distributor. The rotor then routes the energy in order through the spark plug wires ultimately to the engine’s cylinders in order.

The distributor rotor and cap keep the distributor’s contents separate from the engine and keep the distributor’s working parts clean and tidy – while supporting the incredibly high volts of energy and delivering them to the appropriate spark plugs. The spark plugs utilize the spark from the distributor to ignite the fuel mixture, which is what keeps the engine running.

High voltage runs through this entire distributor system during the operation of your vehicle, but this voltage won’t get distributed to the correct spark plugs to ensure that your engine will run. Usually a faulty distributor rotor and cap will produce a few symptoms that can alert the driver that service may be required.

1. Engine misfires

Engine misfires can occur for a number of reasons – checking your distributor rotor and cap to see if they need to be replaced may be one way to ensure that everything is in solid working order so you can check this difficulty off the list.

2. Car doesn’t start

When the distributor cap isn’t on tightly or it is malfunctioning, the engine is unable to send the spark through the entire circuit required to move the cylinders – which ultimately make the car run.

3. Check Engine Light comes on

Your Check Engine light can mean any number of different things, but when you see this light on along with some of the other symptoms listed here, it’s time to call a professional to see what the code is from your car’s computer.

4. Excessive or unusual engine noises

Your vehicle may make some very strange noises if the distributor rotor and cap are malfunctioning – specifically because the cylinders will be trying to fire but failing.

Any time you are having routine servicing on your vehicle, ask that the ignition system be checked. If you have any trouble starting your car get immediate assistance from a qualified professional.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...

Related questions

Q: Car won't start

Hello. If you are able to "turn over" the engine (using, say, the starter motor) but the distributor rotor is stationary, that means the gear on the distributor shaft is sheared off. However, you are also indicating that the battery...

Q: Parking Brake?

The rear parking brake shoes may be causing the clicking inside the new rotors. If the parking brakes are dragging a little. You may have rear brake pads or front brake pads moving inside the caliper bracket. It could also...

Q: Car not starting after performance chip install

Hi, your car may be in anti-theft mode. The system may not recognize your key. The ani-theft mode and wiring may also be defective. In order to have this issue properly diagnosed, I would have a technician come and inspect your...