How to Tell if a Spark Plug is Misfiring

It would not be wrong to say that this tiny fragment has a big job to do. Spark plug serves as a basic ignition source for your car.

If we put an eye on the detailed process, the spark plug provides the core ignition to the air/ fuel mixture the ignition results in a tiny explosion. The entire process, in turn, provides power to the engine, which makes it work fluently.

How to Tell if a Spark Plug is Misfiring?

It is extremely important to get the spark plugs checked frequently or else you may need to replace them. One of the major symptoms of the spark plug misfiring includes rough idling. However, uneven power while accelerating and increasing exhaust emissions are the symptoms to tell if your spark plug is misfiring.

Well, how to know if a spark plug is misfiring? This is what you might be thinking right now! Let me tell you, a bad spark plug majorly leads to messed up the sound of the engine. The sound usually becomes extremely rough. Moreover, you may also feel the vibratory car, whenever you put it to a start.

What happens when spark plugs go bad? No need not to get impatient. Keep reading ahead to know more about the possible symptoms.

Spark Plug Misfire Symptoms

There can be other symptoms as well, which you might come across. A few of them would be currently unfamiliar to you.

To look for the bad spark plug symptoms, follow the list of some other symptoms given below.

  • Check engine light came on
  • The car has trouble starting
  • The car feels sluggish when accelerating
  • High fuel consumption
  • Rough idling

1. Check Engine Light Came ON

Engine light is one of the common symptoms of misfiring, but it may happen due to several other reasons as well. How to know you have a misfiring spark plug?

A bad spark plug causes the engine to misfire. This, in turn, triggers the engine light to turn on. A stable check light notifies an inappropriate functioning going on.

However, if the check engine light comes on and off, that could mean alarming misfires are taking place and demand an immediate fix.

How long can you drive with check engine light on?

You may want to have an estimated duration at hand. But can I be totally honest with you? it’s already too late you cannot drive it when the light starts blinking. Until then, it gets too late to do anything. Just tow it to the desired location. 

2. The Car has Trouble Starting

There might be many possible reasons for your car not starting up. Out of all, one potential reason could be the misfiring of the spark plug. Since these plugs do the job to provide sufficient ignition, misfiring does not produce enough sparks.

This reduction in the sparks, required to power up the engine, results in trouble to get the vehicle starting.

3. The Car Feels Sluggish When Accelerating

Lack of acceleration is another common symptom of spark plug misfiring. If your car is taking too long to put itself together, it’s time to notice it more clearly.

To put it simply, is your car not responsive as previously? Is it taking quite more time to pick up speed? This is majorly due to a misfiring spark plug working in the background.

If you face any such issue, it’s time to get these tiny spark plugs quickly replaced. Since this era demands fast and exotic vehicles, no one likes to have lazy and sluggish cars.

4. High Fuel Consumption

As per the report given out by ASE (National Institute for Automotive Service Excellence), a misfiring spark plug increases fuel consumption by 30%.

It means if have to fill in the gas tank more frequently than usual, it might be due to worn-out misfiring spark plugs.

A car with misfiring spark plugs is high on gas mileage because it does not effectively burn the fuel which powers the engine. Commonly the reduction takes place due to incomplete combustion.

5. Rough Idling

Usually, a car runs at a smooth pace, with appropriate speed, and no noticeable vibrations at all. If your vehicle has any of the symptoms mentioned above, it typically indicates faulty spark plugs.

Misfiring spark plugs cause a car engine to make rough sounds and tend to vibrate when you keep it at idle.

6. Engine Misfires

Engine misfiring is another primary symptom of a defective spark plug. One noticeable cue occurs in the form of engine stumbling. Your engine may halt and then continue with its usual pattern.

It is particularly because the engine is not functioning properly. It highlights that one or more spark plugs are not sparking correctly, which may lead to an increased amount of emission.

A misfiring spark can also damage the catalytic converter. It begins by dumping a large amount of fuel into the exhaust, which becomes overheated and leads to additional damage.

What does a Spark Plug Misfire Feel like?

If a spark plug is misfiring, it can majorly sense by rough idling. Apart from it, misfiring can also feel like the loss of power, engine stumbling, and vibration. A spark misfiring is also sensed by a smell identical to that of oil burning.

You can also feel it by closely listening to a spark plug misfire sound. Faulty plug results in sounds like popping, sneezing and backfiring.

Why Oil in the Spark Plug Well is Causing a Misfire?

Misfiring majorly happens when the oil sweeps down into the spark plug well. The oil makes its way to the well by the center portion of the cover gasket/valve cover gasket.

Once the oil makes its way to the wire, it ruins the spark plug wires in there. This ultimately compels the wires to short themselves out on the walls of the spark plug well. Hence, this results in misfiring.

What to do when Engine Misfires After Changing Spark Plugs and Coils?

Sometimes, even misfire after spark plug change occurs. It may happen due to many conditions. However, the main concern is to understand how to fix this issue?

Check all the wires and if you doubt the connector, get it replaced. Check all the injectors, coils and hoses. Furthermore, check the functioning by swapping the misfiring plug and coil from alternative sides of the engine.

If you still find no clue after the plug swap, try inspecting the cylinder. Try to fix the issue by checking the wiring and connector plug carefully since these wires have the ability to get displaced while replacement, recheck the wiring.

Has nothing worked out for you yet? Try commencing compression test on all cylinders. It can help you in identifying if any one of them is causing the issue.

You can also try cleaning the throttle body and double-check the spark plug gap that can be closed up during handling.

See the latest price of OTC Cylinder Leakage Tester Kit

How to do a Compression Test on an Engine?

You need to start by warming the engine and bringing it to its operating temperature. Now turn off the engine and remove all the spark plugs. Move along by disconnecting all injectors and ignition coil.

Once you are done, the next step is to build compression. The first step is to screw the compression tester into a spark plug hole and crank the engine. By cranking, it merely means to rotate the engine at a sufficient speed to power itself. Don’t forget to hold the throttle wide open while cranking the engine.

During a compression test, you have to abide by the factory specified specs. What’s even more important than this, is to notice the consistency between individual cylinders.

If you come across a cylinder that gives a highly varied reading than others, it’s time to pay attention. Under such circumstances, you require expensive repair due to faulty piston rings or sticking valves.

See the latest price of INNOVA Compression Tester

Related Article: What size is a spark plug socket?

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