Bad Distributor Cap & Rotor Symptoms

Bad Distributor Cap and Rotor Symptoms & Replacement Cost

As you might already know, the distributor cap and rotor play an important part in the process of the internal combustion. For sure, you will not like a car with a deteriorated cap and rotor. If you get a manifestation of it, then you should know that it can create a lot of issues in your engine, as well as the general workability of the car. Nevertheless, bad distributor cap symptoms can manifest anytime in your driving; thus, you should be cautious.

Ten Bad Distributor Cap & Rotor Symptoms

1. Engine misfires

Engine misfires happen due to several reasons. However, the safest area to check for once this problem happens is the cap and rotor. Inspect the cap as well as the rotor to determine if they are already subject to replacement is one approach to guarantee that everything is performing as they should.

2. Car won’t start

If the cap is not firmly on or not working as it should, the engine cannot deliver the spark to the whole circuit needed to make the cylinders act – which conclusively stimulates the operation of the car. Even more particularly, there is a difficulty starting the car when in low temperatures or cold weather.

The low temperatures freeze the distributor, and the abrupt blowout of heat if running the engine triggers the cap to accrue cracks and ultimately break. Nevertheless, you can prevent this case generally by keeping the car from excessive temperatures or weather. 

3. Stalling

If you notice that the car starts easily, it is because of a faulty cap. Because the cap has the rotor that revolves the voltage, is should naturally perform properly. Being clogged, with a chink, or anything that prohibits the rotor from revolving, it can only operate at a certain time.

4. A problem in turning over

Occasionally, you will observe that when stalling, the vehicle turns over. This normally occurs if the engine is either cold or hot. Nevertheless, the problem happens only if there is a problem with the cap. Should you discover that there is no problem with the cap, there could be an issue with another element in the distributor.

5. Check Engine Light is on

The Check Engine Light indicator could mean several things. However, if you notice this indicator along with other manifestations enumerated here, it will be time to contact a skilled person to identify the code from the computer of the car.

6. Unusual or Too Many Noises on the Engine

Your car could manifest several unfamiliar noises, particularly if the rotor and the cap are not working as they should – especially because the cylinders will attempt to excite but break down. You may notice a knocking, stumbling, or metallic sound once the rotor and the cap are deteriorating.

7. Shaking

You may encounter too much vibration or 'shaking' if running or turning the gears. It is normal to notice shaking if you are running the engine or if you are switching gears, particularly for vehicles with manual transmissions.

Nevertheless, irrational shaking while the car is running could imply that there could be a problem with the engine. It is even more disquieting to encounter a much intense shaking that is noticeable in the entire vehicle. The issue could be more distressing if you sense the vibration all through the car. This occurs because of the broken cap. Do not take this problem for granted.

8. High-Pitched Wailing

Another symptom for bad cap and rotor is the high-pitched wailing noise, which happens if starting the car. If the rest of the parts of the car is likely working fine, bring it to stop and inspect the cap.

9. Irregular RPMs

If the RPMs are likely off, then you should have the distributor checked. This manifestation is commonly a symptom that the wires in the distributor have been damaged.

The cap may be eroded, burned, or destroyed. You may begin to address this concern by checking every wire.

10. Backfiring

Considering that backfiring occurs mainly because of the improper firing order, it can be originated from the distributor. Nevertheless, it is necessary to know and understand that backfiring can be triggered by a wide problem. Hence, the backfiring of the engine can be caused by many factors. Two common factors are reduced fuel pressure and limited valves' timing.

NEXT READ: Bad Fuel Pressure Regulator Symptoms and Replacement Cost

The Distributor Cap and Rotor Replacement Cost

If the engine is operating, the ignition coil creates a high voltage that sails from the coil wire going into the rotor. Once the rotor piles in specifically in the system’s distributor, a spark is delivered by the rotor by transmitting it through a coordinated pattern via the wires of the spark plug going to the plug itself, which is positioned in every cylinder of the engine.

The distributor serves as the primary element of the car’s ignition system. The distributor creates an extremely high voltage, which is delivered to ignite your spark plugs.

When changing the distributor, the whole ignition system must undergo an inspection. Once you are done with the replacement, the wires in the ignition should be reinstalled.

If you have to change the cap and rotor because of their poor performance, you can condition yourself to shell out an amount that is around $80 to $120 when getting a new one. The amount will comprise the cost of labor and parts.

Parts could range from $30 to $60, while the cost of labor ranges around $50 to $60. As you could assess it, this job is not a very costly replacement. However, you should still be ready to shell out an extra amount for some fees and taxes, aside from the accumulated estimated cost.


These are the common bad distributor cap symptoms. Now that you comprehend the impacts of a poor distributor, you then realize why it is necessary to care for your car. Any time you schedule the routine service of your car, always specify to the technician to inspect the ignition system for problems or defects. If you encounter any difficulty starting your vehicle, find assistance from a professional automotive technician. Be attentive to what your car is trying to tell you and learn to respond quickly.

Last Updated on: 10/09/2020

About the Author JamesL Davis

James is a certified auto technician specializing in commercial vehicles. With 30 years of experience under his belt, James has encountered almost every type of automotive issue there is! Besides his day job at the repair shop, he is also an amateur race car driver.

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