Bad Distributor Symptoms (Causes, diagnosis & Fixes)

You likely have a distributor if you own one of these older cars. A distributor is a mechanical and electrical component that transmits current from the ignition coils to the spark plugs at the right time for proper combustion.

A failing distributor means that one or more spark plugs will not properly combust the air-fuel mixture once it enters the combustion chambers. The common bad distributor symptoms are hard starting, car not starting, and engine misfiring, but there are other signs you should watch out for.

In this article, you’ll learn the symptoms of a bad distributor cap, how to test a bad distributor cap, and how much to fix it. By the end, you’ll learn how to replace it. So, grab a seat while I walk you through all you need to know.

Bad Distributor Symptoms

Common Symptoms of bad Distributor

Since the distributor plays an essential role in the combustion process, it has apparent symptoms when it fails. Here are bad distributor symptoms in Honda and other car models.

Car not starting

The combustion process must be complete for a car to start and run as predefined by the manufacturer. When you crank the engine, the car battery supplies electric power to the starter motor. The starter motor spins the engine. As the engine spins, it draws air-fuel mixture into the combustion chamber. The pistons compress the air-fuel mixture, and the spark plugs ignite them and cause the momentum that moves the vehicle.

If the distributor fails, it won’t supply enough electric current to the spark plugs, which is needed to ignite the air and fuel in the combustion.

Although several other issues like lousy fuel pump, dead spark plugs, alternator, fuel injectors, ignition switch, starter motor, etc., can prevent your car from starting. So, you should always diagnose your vehicle whenever you experience car not starting issues before replacing the distributor.

Stalling engine

If the engine eventually starts and it has trouble running, it is one of the symptoms of bad points in a distributor or bad rotor. The distributor has a rotor that rotates to supply electric flow, and the rotor must work fine for the vehicle to run smoothly.

If the rotor cracks or clogs with carbons, it may prevent it from rotating, which will not only cause engine stalling, it may lead to engine backfiring. Plus, clogged contact points will cause stalling and engine misfiring.

The illumination of the check engine light

The powertrain control module triggers the check engine light on the dashboard whenever it detects a problem in the powertrain. The engine firing cycle is one of the things the PCM monitors. If the distributor fails, the spark plugs will not ignite the fuel properly, causing the car computer to trigger the check engine light on the dashboard.

Additionally, if the distributor timing is too advanced or retarded, it’ll affect the engine firing cycle. When this happens, the car computer will trigger the check engine light on the dash to notify the driver of an underlying issue.

Your vehicle is vibrating

Several factors, like lousy engine mount, damaged transmission mount, wheel, and tire issues, can cause car vibration. However, vibration is one of the bad distributor symptoms in Chevy 350 and other car models. Plus, vibration can result from a misfiring engine.

Squealing noise from the distributor

Another common bad distributor symptom on 5.7 Vortec and other car models is a squealing or high-pitched noise from the distributor. This unique sign lets you know when the distributor is failing.

To confirm if the sound is coming from the distributor, remove the screws holding the covers and inspect it. The high-pitched noise comes from the distributor if you see a build-up of carbons, dirt, grease, or other contaminants.

Failed smog inspection

The distributor provides electric flow to the spark plugs but if it fails, the plugs may not provide enough spark to properly burn the fuel in the combustion chamber. The unburnt fuel will exit the combustion chamber alongside exhaust gas, which will cause you to fail emission inspection.

symptoms of a bad distributor shaft

How to Check Bad distributors

If your vehicle uses a distributor and you notice one or more of the above signs, you have to check the distributor to ensure it is the root cause of the problem before blaming it.

Here’s a simplified step on how to test a distributor to know when it is faulty.

  • Locate the distributor in the engine bay, close to no.1 or 4 cylinder on four-cylinder engines. It has plug wires that connect to the spark plugs.
  • Unplug one of the distributor lead wires and place a screwdriver very close to it to create an arc. Avoid doing this with your hand to avoid injuries.
  • Unscrew the bolts holding the distributor caps and inspect them for signs of cracks, damage, and corrosion.
  • Ensure the firing points are not covered up with build-ups. Bad contact points will look corroded or burnt.
  • Ensure the rotor is in good condition.

What causes distributors to become bad quickly

Like several car components, some factors can cause the distributor to become faulty. Here are the most common causes you should watch out for.


Corrosion is a common issue with most electrical components in cars. It occurs when moisture and a metallic component come into contact. It can also happen due to oxidation when your vehicle runs too hot. Other substances, like grease or deposits, fuel or oil leaks, can cause corrosion.

You can protect your car distributor from corrosion by cultivating a regular maintenance habit.

Carbon build-ups

Carbon build-up is the most common reason distributors become bad quickly. High electric flow spark in the distributor can cause build-ups and erosion on the contact points, rotor, and other parts. Carbon build-ups are typically obvious. You can see them once you remove the distributor caps.

Wear and tear

Distributors are subject to wear and tear since they are exposed to high electric voltage. Plan on replacing it every two to three years so it won’t fail when you least expect it.

bad distributor symptoms chevy 350

How to fix bad distributors?

If you establish that you have a lousy distributor after a thorough inspection, you must fix or replace it, depending on the type of damage.

If it’s a cracked distributor cap, replacing it with a new one is the most feasible fix. But if the cap is dirty or corroded, you must clean it properly. Here’s a simplified guide on how to clean a corroded distributor.

  • Remove the distributor cables. Ensure they are labeled. If not, label them so that you can reinstall them in the correct order.
  • Remove the distributor cap by unscrewing the fasteners holding it in place
  • Clean the contact points on the distributor cap with a bristle brush and some contact cleaner
  • Dry the cleaned cap with compressed air or a clean rag
  • Reinstall the distributor cap by following the reverse process.

If the problem persists after cleaning the distributor, replacing it would be the only option. To replace it, remove the lead wires, the distributor cap, and the lousy distributor. After that, lose the bolts holding the distributor in place. Install the new distributor using the reverse procedure. However, this type of job is best left to professionals because you have to time the distributor with the engine using the manufacturer’s specifications.

Frequently Asked Questions – FAQs

Q: Can a bad distributor cause loss of power?

Distributors are an integral part of older vehicle engines. If they fail, they’ll cause several issues like the car not starting, hard starting, engine stalling, unresponsive gas pedal, loss of power while driving, er, and can get you stranded in the middle of nowhere. So, it is essential to fix distributor issues before it drops expensive repair bills.

Q: How do I know if my distributor timing is off?

The engine will experience problems if the distributor timing is off. Some of the issues that let you know when the distributor timing off include the following;

Poor gas mileage: The timing of the plugs is essential for a complete and seamless combustion process. If the distributor timing is off, the spark plugs may not fire when they should. And if this happens, the car computer will try to compensate by adding more fuel into the combustion chamber. This will invariably lead to high gas mileage.

Low engine power: If the distributor timing is too retarded, the spark plugs will fire too late, leading to low engine power output.

Misfiring engine: Your engine will misfire if the spark plugs are not firing when they are supposed to due to retarded or advanced distributor timing.

Q: Will a new distributor improve performance?

Professional engine builders and old gearheads agree that replacing your distributor with a high-quality one made for the vehicle will significantly enhance your engine performance. You’ll enjoy a seamless and smoother driving experience, and the engine will perform well at all RPMs.

Q: Can distributor timing cause no start?

Wrong distributor timing is one of the most misdiagnosed and overlooked reasons a car won’t start. The distributor timing controls when the plugs should ignite the fuel in the combustion chamber during a compression stroke. Of course, this is important to start a car, but you should know that several other factors can prevent a car from starting.

Q: Should I replace the distributor or just the cap and rotor?

I recommend you replace the distributor cap and rotor when changing the spark plugs. Typically, the contact pins in the distributor and the rotor wear out at the same time as the spark plug electrodes. This will help the distributor to last long. However, if the distributor shaft is worn out or broken, you must replace the complete distributor.

Q: Can the distributor cause rough idle?

A lousy distributor can cause various problems, including engine stalling, misfiring and backfiring, unresponsive gas pedals, high-pitched noise when the vehicle is running, rough idling, and other engine drivability issues.

Q: What are the symptoms of worn distributor gear?

Symptoms of a bad distributor shaft can cause unnerving and frustrating situations for the car owner. These issues include high-pitched or squealing noise from the distributor, no start conditions, hard starting, misfiring and backfiring, engine stalling, and shaking.

Q: Can I drive with a bad distributor?

While you can drive with a bad distributor, you shouldn’t. A faulty distributor can cause engine misfire, stalling, and other issues, which can be dangerous if it happens when overtaking a car on the highway. Plus, a bad distributor can affect other engine components, like making the catalytic converter run hot.

Final Words

If you have been reading to this point, you will no longer ask, do distributors go bad? Car distributors can fail due to wear and tear, corrosion, and carbon buildup. When it starts failing, it’ll leave some bad distributor symptoms to tell you something is wrong.

Fortunately, all you need to address the issue could be to clean it. Once you notice any symptoms of a bad distributor, diligently check and fix it by following the steps listed above.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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