Updated at: 23-07-2022 - By: Lucas

The spark plugs’ job is to ignite the cylinder’s working mixture. Plugs that are worn will have an impact on the engine’s performance in exactly the same way. At worst, a defective spark plug prevents any ignition from taking place in the working mixture at all.

Check and replace spark plugs according to the car’s service manual. Most people don’t even bother to inspect the spark plugs until a certain mileage is achieved.

Identification and replacement of damaged spark plugs are essential to ensure proper operation of the fuel system and engine.

Rough idle engines are a major source of frustration for many people today. Find the root cause as soon as possible in order to prevent more faults and damages from taking place.

Having said that, many new car owners may wonder if their spark plugs are causing their car to sputter.

The answer to this question varies from one automobile malfunction to the next, depending on the car and the conditions.

Here are a few things to keep in mind when you conduct your investigation in order to arrive at the correct conclusion.

The first thing to know is that many distinct factors might contribute to a rough idle in a vehicle. The spark plugs can also be the source of this type of engine issue, of course. As a result, the following should be clarified for your benefit:

What should you check first when you have a rough idle?

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Rough idle can be caused by a variety of factors, as previously discussed. The causes listed below are some of the more common ones.

  • Idle speed needs adjusting
  • Malfunctioning fuel pump
  • Loose or dysfunctional distributor cap
  • Worn out spark plugs
  • Dirty fuel filter
  • Clogged fuel injectors

The causes of a car’s sluggish idling are numerous, as evidenced by this list. Before you can conclude that your spark plugs are to blame for your car’s harsh idle, you’ll need to figure out what’s causing it.

So, let’s take a look at what’s going on and then see how your spark plugs are doing. Additionally, this article will address several other reasons that may be contributing to a sluggish engine idling.

Note the conditions when your rough idling occurs

You might wish to start by making some notes. These notes can be helpful in narrowing down the scope of a problem to be diagnosed. When you hear a harsh idle, for example, you need to know what exactly is going on.

Is it still early in the day?

If you restart a warmed-up vehicle, does it run rough?

Regardless of the circumstances, a cold start could be caused by a variety of issues, including a vacuum leak or faulty spark plugs. It’s also important to observe the computer code shown if it is a newer model car.

For your own troubleshooting, you can use the notes you take. Alternatively, you can share your observations with a mechanic who has to delve deeper to find a solution to your idling issues.

Check Your Spark Plugs: Manually or with the Use of a Multimeter

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As a first step in troubleshooting, if you suspect that your vehicle’s rough idling is related to your spark plugs, you can investigate these issues. Also, here are some things to look for.

Do a manual Inspection of your spark plugs to see if they are old, worn out, dirty, bad, or failing.

To begin, remove each spark plug one at a time and inspect them for damage. However, in order to make this determination, you must first be familiar with the appearance of a typical spark plug. Normal spark plug electrode surfaces will show grayish tan or brown deposits, for example.

Soot on the electrodes and insulator tip of the spark plug is an indication that the vehicle has been driven excessively at low speeds or has been idling for an extended period of time.

Either way, this usually means you need to get new spark plugs immediately away.

Use a digital or analog multimeter (or ohmmeter)

Since there are many ways to verify the condition of your spark plugs, it’s a good thing. In addition to visually inspecting the spark plugs, a multimeter or ohmmeter can be used to verify that the resistance is within the manufacturer’s specifications.

If not, it will be necessary to replace the old, corroded spark plugs.

What Happens if the Spark Plugs are failing and going bad?

The electrical combustion mechanism of the engine relies heavily on the spark plugs. Keeping the engine operating smoothly instead of rough is one of its key functions.

It’s therefore possible that the spark plugs may need to be replaced to fix the problem of a stuttering engine.

Spark plug replacement costs between $195 and $251 on average, so it’s crucial to keep that in mind as well. Labor costs between $125 and $160, with parts costing from $65 to $95 on average.


Spark plugs may cause harsh idling.

Yes, especially if the sparks in the engine have gone out of service. As a result, if you suspect that this is the cause of your car’s idling issues, you should begin your diagnostic process with this in mind. If this is the primary cause of your car’s rough running, simply replacing the spark plugs will restore your vehicle’s smooth operation.