What Does A Bad Distributor Rotor Look Like? [Explained]

Owners of older motor vehicles often run into many issues with their cars. Your car might be old. Then it is almost certain that it uses a distributor. A faulty distributor may mean your vehicle doesn’t function at its peak capability.

So before you try and diagnose the issue, you should ask what does a bad distributor rotor look like?

The easiest way to determine a bad distributor rotor is by its sound. On a rainy day, the most common symptom is shaking or whirring of the engine. Screeching noises can also be heard. The dashboard lights up as the check engine light turns on.

We look at the telltale signs of a bad distributor cap and issues with rotors. We also inform you how to fix your distributor cap and rotor in 4 easy steps.

So keep on reading! 

What Happens With A Faulty Distributor Rotor?

It basically depends on what’s wrong with the distributor rotor. Sometimes the conductor spring can break. It will block the sparks to reach the plugs. The rotor is a relatively simple part. It transfers the high voltage coil out to the right spark plug terminal.

Here we have listed some essential signs of a bad distributor rotor.

Car doesn’t start

Sometimes the distributor rotor malfunctions. As the engine does not send the spark through the circuit, problems arise.

A malfunctioning rotor causes engine misfires. Misfires cause the cylinders to function in a desynchronized manner. This in turn makes the engine fail before it starts.

Engine Light Comes On

The check engine light goes off by a lot of triggers. But this coupled with the reasons on this article indicates something obvious. A problem with the distributor cap or the rotor to be exact.

Weird Engine Noises

When the engine starts, the mistimed firing of cylinders can be heard quite clearly. When the distributor rotor malfunctions, your cylinders misfire. Thus, your car makes some very weird noises.

The distributor cap encapsulates the rotor. Failure of the rotor also busts the cap. This causes the whirring noises, and indicates the cap is failing.

Having a routine check on your ignition is essential. This is to detect any defects in the distributor cap or rotor. Automotive technicians can easily diagnose these problems with older vehicles.

The Spark Plug malfunctions

When you turn on your engine, it sends a spark of electricity to the rotor. This makes the rotors turn inside the distributor. The rotor sends the electricity through spark plugs. Which eventually leads to the engine cylinders.

The distributor cap keeps the distributor’s content separate. Separates it from the rotors and the engines. It keeps the high voltages of energy from reaching. The wrong parts of the engine. Delivers the volts appropriately to the spark plugs. 

The spark plugs use the sparks arriving from the distributor. It basically helps to light the fuel. This is what keeps the engine running. 

Engine Misfires 

Engine misfires can happen for a lot of reasons. The distributor rotor misfiring causes desynchronized sparks in the plug. This causes faulty currents to flow through the circuit.

Sometimes it can also cause engine idling. Idling means running the engine while the car is not moving. Cracking causes vibrations during idling. Also, a bumpy acceleration when you hit the pedals.

What happens ultimately is the failure in transmission. All in all causing the cylinders to also fire faultily, thus generating misfires.

Acceleration Issues

A distributor rotor’s proper functionality is essential. It is important for the combustion engine. Thus a bad distributor rotor would essentially cause starting problems.

A cracked distributor cap and rotor cause combustions to be mistimed. This causes hiccups, and hesitation during acceleration. If the rotors are completely busted, the spark plug would fail. While starting the engine altogether.

Vibrations and Backfires 

If you’ve got a bad distributor rotor, you will experience some extent of vibrations. The rotors cause backfires in the engine. This can even lead to violent shaking of the vehicle if left unchecked.

The reason for this being the distributor rotor not spinning properly. The cap doesn’t send correct voltages to the right cylinders of the engine.

This in turn messes up the timing. And causes what is compression malfunction. The cylinders fire back with force, thus a backfire is produced.

If you notice this kind of vibration on idle, it’s bad news. The diagnosis is almost always a faulty distributor cap and rotor.

How to Fix a Bad Distributor Rotor

There are a few ways to fix a bad distributor rotor. Such as fixing and cleaning the rotor. If it’s too bad you may have to get a new one. A few easy steps to fix a bad rotor are given below.

Fixing a cracked distributor rotor

A cracked distributor rotor or cap causes rough idling, engine misfire. It also creates cracking noise and severe vibration.

To prevent this you need to inspect the distributor cap. This must be done on a regular basis. In the winter, park your car where it doesn’t snow. That way it would take little damage from the weather.

If your cap has already cracked, unfortunately, there’s only one option. And that is to replace it. Distributor caps come by cheap, same goes for the rotor. 

All you need to do is replace them if they’re cracked. But it is essential you do so.

Fixing dirty or corroded distributor rotors

Distributor rotor and cap terminals are corroded due to water vapor contact. If the distributor shaft reaches the camshaft gear, it’s bad news. 

The water vapor used to cool the engine down causes corrosion. Excess moisture overcharges your battery. The battery acid builds up in tubes and is transported to the distributor. 

The tubes and wires may be porous. Which also causes moisture to seep into the rotors. The distributor caps and rotors are also prone to collecting dirt. This grime ultimately makes its way into the system through transmission. 

So, how to fix these?

Here are 3 easy steps to fix your dirty or corroded distributor rotors!!

Step 1: Label and clean spark plug cables: 

Firstly, You remove the spark plug cables. Reassemble after cleaning. This is made easier if you label them.

Step 2: Clean the terminals: 

Use a soft bristle brush. Strong enough to remove carbon build-ups. This means it is also abrasive enough to remove oxidation. Once you have removed the corrosive buildup. Spray some lubricant or cleaner (contact to be specific)

Step 3: Dry the cap

Use a rug/ air compressor to dry the cap completely. This helps remove any moisture or lubricant dripping on the rotor.

And you’re done!


Can a bad distributor cause loss of power?

Yes, bad spark plugs and plug wires coupled with cracked distributor rotors causes power loss. A faulty distributor cap causes spark/compression loss. Meaning too much of the fuel mixture flees.

The air and fuel mixture leaving before combustion causes engine misfires and loss of transmission.

Can a bad distributor cause overheating?

Yes, when there are engine misfires. The engine fails to decompress hot air in time. The mistiming can cause the cylinders. To have a spark failure and overheat. This means the whole engine will eventually be too hot to handle!

How much does it cost to replace a distributor?

The distributor cap and rotor replacement can cost upward of $70 upto $130. This includes the parts. As well labor costs of the mechanic. Unless you do it yourself. It is recommended you get it done through an auto shop. Unless you’re truly experienced.


We hope by now you better understand what does a bad distributor rotor look like. Hopefully, this article answered some of your burning questions.

To know if your vintage engines are up to gear, you should get it checked. A bad distributor rotor can mean death to a lot of great cars. Make sure yours isn’t one of them!

Thank you for reading!

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