Bad Distributor Symptoms

Bad Distributor Symptoms – How To Spot A Failing Distributor

A faulty distributor can reduce the efficiency of your engine by wreaking havoc on the ignition. The distributor is an integral part of the ignition, and therefore, any faults in it can affect your car in adverse ways. As we look at bad distributor symptoms, it can have severe effects ranging from rough idling, shaking, and even stalling.

There are many reasons why a distributor can develop problems. Some of the most common reasons include wear and tear over time. The distributor is also prone to developing problems because of the harsh environment it is located in. However, before we delve more into bad distributor symptoms, it is prudent you first understand how a distributor works.

How A Distributor Works

The distributor plays a critical role in the ignition process. It transfers high voltage from the secondary coil to the right spark plugs at the correct interval and in the correct firing order. Taking a closer look, the distributor handles several tasks. The first task is done by the distributor cap and rotor.

They transfer high voltage from the coil to the right cylinders. The secondary coil is connected to the distributor rotor, which happily sits on the distributor cap. The ignition coil is connected to the rotor by a spring-loaded brush. The electric current produced by the engine turns the rotor.

Without making any contact, the rotor distributes high voltage to a series of contacts as it spins. The high voltage pulses run down the spark plug wire and transfer to the correct cylinder. This precision is crucial to achieving optimum engine performance and efficiency.

Over time, this arcing causes the rotor and cap to wear out. This is why they are both replaced when you are doing a tune-up. The spark plug wires may also wear out with the distributor and cause some very mysterious engine issues. If you own an older model car, it may have a different type of distributor. These older engines came fitted with distributors that had breaker points.

If any malfunctioning develops in the distributor parts, the spark plugs won’t receive the necessary spark. This means the spark plugs won’t be able to ignite the fuel mixture. In turn, this will affect your car engine’s ability to distribute power efficiently. A faulty distributor is the beginning of a car’s starting problem and a host of other performance issues.

Common Bad Distributor Symptoms

As you are now aware, the distributor may be a small part, but it plays a critical role in the working of a car. For sure, a car with distributor problems is not something you would want in your possession. However, such problems do develop, even when you are driving. It is therefore important that you learn to spot a faulty distributor before the problem escalates further. Here are eight of the most common bad distributor symptoms.

Bad Distributor Symptoms

1) Car Won’t Start

If the distributor cap is not working as it should or is not firmly on, your car may not start. This is because the essential spark needed for combustion is not being delivered. Without the spark being delivered to the spark plugs, the engine won’t run. Apart from the cap, a faulty rotor or shaft can also prevent your car from starting.

This is particularly evident in the cold season when most starting problems manifest. In low temperatures, the distributor parts freeze. The abrupt heat surge causes the distributor cap to develop cracks when you attempt to start the car.

The cracks will ultimately lead to breakage. This case is particularly common with cars that are parked outside. Cars that are parked in unheated garages with low temperatures are also prone to starting problems.

2) Engine Misfires

Sure, many engine problems may manifest in engine misfires. But a faulty distributor is one of the most common reasons for engine misfires. If you are experiencing engine misfires, the distributor is the safest place to check first. Thoroughly inspect the cap for any cracks as well as the distributor rotor. Typically, engine misfire is a sign that the rotor and cap are subject to replacement.

A misfiring engine feels like it’s stumbling. Misfiring occurs when the distributor cap fails to supply enough current to the spark plugs. The cap regulates the engine’s firing order, and any malfunction in its parts can be felt in the engine’s performance.

3) Unusual Shaking

Inexplicable shaking, while the engine is running is a classic symptom of a failing distributor. This may range from a light vibration to a more pronounced shaking that can be felt throughout the car. A possible cause for this is a distributor rotor that is not spinning as it should. Also, if the cap does not supply the voltage properly in the right cylinder power stroke, it may shake.

Anything that messes up the firing and timing process in the cylinders causes the vehicle to shake inexplicably. If you have noticed that your vehicle is shaking during idle or coming to a halt, the most probable culprit is a faulty distributor. The shaking can also be prominent when shifting gears or starting the vehicle.

4) Stalling And Backfire

Backfiring from the exhaust or stalling while coasting with the car is another telltale sign that your car has a bad distributor. The car backfires or stalls when the engine loses power due to improper combustion. If your car stalls a few seconds after starting the engine, you are most probably dealing with a failing distributor.

As we mentioned earlier, the cap must deliver enough voltage to the spark plugs for internal combustion to occur. If the rotor is not turning properly, the engine will not achieve optimum combustion. A crack on the cap or clog in the distributor can stop the rotor from spinning properly. This may result in a backfiring situation or stalling.

5) High Pitched Squealing Noises

Another common symptom that the distributor is bad is high-pitched noises from the bearings inside the distributor. Typically, you will hear the squealing noise when starting the engine. A bad distributor produces a unique squealing noise that can be easily distinguished from other engine noises. If you hear such a sound from the engine bay, check under the distributor cap.

Generally, a distributor will produce a squealing noise when it’s caked with grease and other pollutants. These buildups cause blockage of the air circulation, which in turn produces a high-pitched sound. If the yelling sound persists even after a thorough cleanup of the cap, it’s time to visit your mechanic for a more detailed inspection.

6) Difficulty Turning Over

Along with the engine stalling, you may also notice the vehicle is having a hard time turning over. Typically, the engine fails to turn over when it’s cold and rarely when it’s hot. When you turn the ignition key, the battery delivers electricity to the spark plugs. The resulting spark makes the initial combustion.

The energy generated from the initial combustion turns the crankshaft and allows the car to move. Lack of turning over, which is the movement of the crankshaft, points to issues with a malfunctioning distributor. Most of the time, this is usually the case of a cap that is not intact. If the cap is intact, the problem could be in the timing belt or the crankshaft itself.

7) Check Engine Light

The engine control unit (ECU) will detect an improper combustion process and illuminate the check engine warning light. A bad distributor rotor or cap is one of the common causes of improper combustion. The check engine light will come on if the distributor is not distributing voltage consistently or correctly.

Bad Distributor Symptoms

A cracked or broken cap and a clogged rotor are one of the major culprits of improper combustion. The check engine light comes on if the ECU detects even the slightest instance of messed-up firing order or timing. Of course, many other errors can cause the check engine light to come on.

However, you should check your distributor if you see the check engine light and other telltale signs of a faulty distributor. Most vehicles equipped with a distributor are likely to have been made before the era of the ECU. Therefore, detecting distributor errors can’t be a matter of reading error codes.

8) Irregular RPMs

Irregular RPMs are another common symptom of a bad distributor. If you notice that your RPMs are likely off, have your distributor rotor and cap checked. Distributor wires are also likely to be the cause of your irregular RPMs. If the wires have been damaged, the distributor supplies inconsistent current to the cylinders.

Check if the distributor rotor turns properly and if the cap is burned, cracked, or corroded. If they seem to be working just fine, check every distributor wire.

Diagnosing Bad Distributor Symptoms

If your car shows some or any of the bad distributor symptoms above, it can be a problem with your distributor. However, the symptoms above, such as engine misfires and check engine lights coming on, can be caused by a host of other problems. Engine and ignition system problems can also exhibit similar symptoms.

So, to be more certain about the exact issue your car is having, you’ll have to diagnose and test your distributor. Bad distributor symptoms can quickly escalate to an engine problem if left unaddressed. To avoid future engine problems, the distributor should be tested if the car shows any symptoms of a faulty one.

Tools You Will Need to Test a Distributor

  • A Ratchet
  • A Ratcheting Socket
  • A Magnetic Screwdriver
  • Spark Plug
  • Light Or Spark Tester
  • Multimeter Or Volt Meter
  • A Flashlight

Step 1: Check The Distributor Cap

The distributor cap is the most likely culprit for most distributor problems. Hence, it should be the first place when you suspect you have bad distributor symptoms. As we mentioned earlier in this article, the distributor caps are responsible for making the sparks. Therefore, a working distributor cap should be producing sparks that arc correctly. The surface of the cap should be free from any dirt or grease.

Here is a video on how the sparks arc when you crank your engine.

Then proceed to take the distributor cap off using your racket and socket. This should help you closely examine it for any signs of damage. If you find any signs of rust, erosion, or corrosion, it may be the cause of your distributor problems. Check the entire cap, including the cap rotor, for any signs of carbon traces or burns.

If there are carbon traces in the distributor cap, this could be the problem. Carbon traces misfire a spark between the plugs and may lead to the distributor working improperly. The misfired spark usually ends up as a failed electric connection.

Step 2: Check The Contact Points

If the distributor caps are in great condition, the contact points are next to check for faults. However, you should only inspect the contact points after checking the condenser. If the condenser is damaged or opened, it could mean a broken wire lead. This causes arcing that can lead to severe damage to the engine.

After confirming the condenser is working well, proceed to check the contact points. Damaged contacts can lead to multiple ignition problems. Look for any signs of degradation, corrosion, or any other damage. If they appear burned, consider replacing them. Watch this video on how to test the condenser and contact points of a distributor.

Step 3: Test The Arcing

For this part, you will have to test the spark plug wires. You can use a spark tester to check the arc of your distributor. This can be achieved by placing the spark tester in the metal part of the plug wire and fire the ignition. If the arc is firing, the tester will display a spark sign, and therefore that is not the problem.

If the spark tester does not detect any spark, use a test light to test the coil. Connect the test light to the side of the coil and fire the ignition. If it produces any light flashes, then the coil is not working properly. If you don’t get any flashes or sparks, the problem could be in the electrical wiring of your ignition system.

When the spark tester powers with the coil on positive, it means you have a faulty coil. If it powers on both terminals, it indicates a problem with the contact points. However, if both the negative and positive sides work, it means you’ll have to inspect the ignition wiring further.

Bad Distributor Symptoms: How To Fix

Now that you have established that you are dealing with a faulty distributor, what can be done to prevent further damage to the engine? Your next course of action will be determined by the kind of distributor problem you are experiencing. Here are some of the fixes you can apply to a bad distributor.

Cracked Distributor Cap

A cracked distributor cap should be replaced immediately to reduce rough idling. To prevent cracking, you should regularly inspect the distributor cap for any signs of faults. Whenever possible, avoid parking your car outside during low-temperature seasons. Try and protect your car from freezing conditions as best as you can.

Corroded Or Dirty Distributor Cap

Water vapor can concentrate in the distributor cap and cause corrosion to the distributor cap terminals. This water vapor comes in through the distributor shaft from the crankcase. The water vapor condenses into liquid when the engine cools down. Water reacts with the metallic parts of the distributor contacts and forms corrosion.

The battery is another major source of moisture in the distributor. When charged excessively by the alternator, the battery produces acid that concentrates inside the distributor. If the plug wires are porous, moisture trapped in their insulation casing may end up inside the distributor.

Apart from moisture, the distributor cap is also prone to collecting grime and dirt. Grime and dirt build-ups can easily be resolved using a multi-purpose cleaner like WD40. If you detect a clogged-up or corroded distributor cap, clean it up to restore its functionality. Replace the cap gasket if you notice the distributor cap is loose.

Here are steps you should take to clean corroded or dirty distributor caps

1) Remove The Spark Plug Cables

If the cables are not labeled, label them so that you can put them back in the correct order. After labeling them, gently pull them out from the distributor cap terminals.

2) Remove The Cap

Use a screwdriver to unscrew the cap and gently pull it up. The distributor cap is usually fastened to the distributor with two screws on each side.

3) Clean The Contacts

Now that you have exposed the distributor metal contacts use a soft bristle brush and some contact cleaner to clean. The brush should be soft and abrasive enough to remove any oxidation layer or carbon buildup on the metal terminals. Don’t forget to spray some WD40 on the internal metal contacts.

4) Dry It Out

If you have access to a source of compressed air, use it to dry out the cleaned cap. Compressed air will help dry it out quickly and get out any left debris. However, you can also use a clean rug to rub the distributor cap dry.

5) Put It Back Together

Now apply the reverse of the whole process. Put the cap back into place and fasten the screws on the sides. If the gasket is worn out, it may allow moisture into the cap and cause more problems. Replace it if need be. For further protection, apply a light silicone seal around the cap base. Connect the spark plug wires in the right order as labeled. Crank up your engine to see if the fix applied.

Replacing The Distributor Cap And Rotor

If you have applied the above fixes and still experience distributor problems, it’s best to consider replacing your distributor cap and rotor. You can expect to pay anywhere from $60 to $130, depending on where you get the services. This total cost includes labor costs and purchasing both parts.

Can You Replace The Distributor Rotor And Cap On Your Own?

Most car enthusiasts or anyone with decent car knowledge can save money by doing the replacement themselves. This does not require any sophisticated tools. All you need is a ratchet, ratchet socket, screwdriver, and a good service manual to walk you through the whole process.

The following video contains easy DIY steps on how to replace the distributor. Just make sure to apply the necessary safety precautions like disconnecting the car battery lest you zap yourself.

How Often Should You Replace The Distributor Cap And Rotor?

The distributor rotor and cap are highly prone to wear and tear due to the high voltage they are regularly subjected to. Each time you start your engine, high voltage flows through your distributor. They are therefore bound to wear out with time. The ignition system should also be inspected thoroughly after replacing the distributor parts.

To catch your distributor failing, ensure the ignition system is thoroughly inspected during routine maintenance. However, where you park your vehicle during winter will determine the lifespan of your distributor cap. The distributor is also likely to fail if you keep driving your car through deep puddles. This increases the chances of getting moisture into the distributor cap.

Routine servicing is recommended for most vehicles after every 25000 miles. Regardless of the current condition of the distributor cap and rotor, most service shops will often replace the two parts. If your car is not used often, it is advisable to replace the cap and rotor every two years if they don’t show any bad distributor symptoms.

Bad Distributor Symptoms: Conclusion

The distributor is an integral part of the ignition system. It plays a critical role in the workability of your vehicle. For sure, a bad distributor is not something you would want in your car. A faulty distributor renders the whole car unusable and highly inefficient. Therefore, it is prudent to know how to spot bad distributor symptoms before it escalates to a faulty engine.

However, if it does happen and your car’s distributor fails, it is not the end of the road. Fortunately, you can easily fix or replace a bad distributor with the help of a few simple tools. Some distributor problems may, however, require the intervention of a seasoned mechanic.

Approved Tools

These tools have been tried and tested by our team, they are ideal for fixing your car at home.

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