How to Check Spark Plugs Without Removing Them? 3 Steps

Everybody wants to get the work done, the easy way. In cars and vehicles where keeping up with regular maintenance is so important it sometimes becomes a challenge to remove each of its parts just to make sure its proper functionality. Therefore, today I shall tell you how to check spark plugs without removing them.

Usually the spark plug lasts up to 20,000 miles but the high-quality and expensive iridium spark plugs or platinum spark plugs can last 60,000 miles as well. If your car has long life spark plugs they can last 100,000 miles.

However, it’s important to know what the job of a spark plug is.

In all vehicles and cars, the spark plugs (as the name says) are there to ignite the spark in order to turn on the car. These small plugs ignite the air and fuel mixture in the engine when the timing is just-right. However, the proper function of the spark plug leans on its durability, fuel efficiency etc.

So when you have properly started the car or hard staring occurs it means the plugs are to be removed. If you notice a bad spark plug in your car, here is how to remove it.

Check Spark Plugs without removing them- Here’s how?

Here are the easy and testified ways to check spark plugs without having to remove them.

1. Disconnect the Spark Plugs

Take out the spark plug wires when the engine is still running. It’s very easy to do, however, if the engine is not working, turn it on. Now if you notice the drop in car speed or roughness after removing one of the spark plug wires it means the spark plugs are working fine.

But If you do not notice any change in the engine after removing the wires of the plugs, it means the spark plugs have gone bad, or there is some problem with them.

2. Do Spark Plug Ignition Test

Another way to check spark plug is to do a plug ignition test. Disconnect the spark plug wire and insert the screwdriver by holding the end close to the metal surface. There should be a crackling sound if the spark plugs are in good condition, if not, the plugs are bad.

3. Use Spark Plug Tester

You can try another way for testing by using the reliable spark plug tester.  

  • Turn off the engine and disconnect the negative terminal of the battery
  • Check for the spark plug in the cylinder and take out the boot on the first plug
  • Now press the spark plug tester boot on the spark plug and let it click. After that connect the spark plug boot on the tester and link the wire (spark plug wire) to the tester end
  • Reconnect the engine battery negative terminal and turn on the car (make sure to keep an eye on the spark plug tester, better to ask a friend for help).
  • Now if you see lights are flashing, it means the spark plugs are working fine and are in good condition. But if there are no light flashes it means the plugs are defective and you should replace them.


How many ohms should a spark plug read?

The spark plug tester should ideally read the max resistance level of 12,000 Ohms per foot. This was recommended by the Society of Automotive Engineers. But that is not the rule of thumb, some of the Original Equipment Manufacturers (OEMs) have their dedicated spark plug resistance levels as well.

Therefore, we recommend you to take help from the plugs’ manufacturer’s manual to get the information right.

How do I know the spark plug is weak?

Usually, the weak spark plugs are in orange or reddish coloration due to excessive use whereas the good spark plugs are in blue-white color. Moreover, if your car is working fine and starting right when you ignite it, it means the plus is igniting the spark in an efficient way.


Spark plugs in the car are often subjected to overlooking. As you know the typical lifespan of the spark plug is about 10,000-20,000 miles, so when you don’t replace them even after that, problems may occur due to wear and tear.

However, if you don’t want to take your car to the mechanic, we hope this article has helped you in checking the spark plug without removing them.

Leave a Comment