What should you do after changing the spark plugs?

Though quality spark plugs are built to last long, it’s always recommended to change your spark plugs every 60,000—80,000 miles(96,561—128,748km) or so.

Spark plugs come with a finite lifespan and the correct replacement interval depends on the car you drive.

To get the most functionality out of your newly replaced plugs, you need to do one critical thing before putting the car back on the road.

Notably, this will also help you avoid any significant problems that may arise as a result of not getting the job done properly. Actually, so much could go wrong when you install your new spark plugs improperly, possibly killing your engine entirely.

Having said that, here’s what to do after changing spark plugs;

Start Up Your Engine and Take Note of Its Behavior

Did your engine start as it should without any hitch? If yes, congratulations on replacing the spark plugs correctly. On the contrary, if you noticed an issue such as a rough idle, this could suggest a possible ignition system problem.

In that case, be sure to call in your mechanic immediately. Otherwise, the issue could quickly lead to a more costly repair.

Alternatively, your engine may start up just fine but throw an error code. In that case, you can try to diagnose the underlying issue by yourself before calling in your mechanic.

Here you can use an OBD reader. OBD readers are nowadays readily available, which means you can get one from your nearest automobile tool shop or online anytime you wish.

If it’s an issue you can easily correct, there’s no need to contact your mechanic.

How To Replace Your Car’s Worn Spark Plugs

Generally speaking, replacing spark plugs is a fairly simple process. All you have to do is follow the quick steps below;

  • Disconnect the battery.
  • Determine which wire goes to which plug and where it attaches to the distributor.
  • Take out the old spark plugs and wires, working one plug and one wire at a time.
  • Using your hand, thread the firing ends of the new plugs into their respective empty cylinder heads, screwing in one plug’s firing end into a cylinder head at a time while making sure it isn’t seated improperly or cross-threaded.
  • Using a torque wrench, torque each spark plug down to the specified torque and attach the new wire. Repeat this step for the remaining plugs.

What Could Go Wrong If You Replace Your Spark Plugs Wrongly?

As you can see, replacing spark plugs is a relatively simple procedure that entails only five straightforward steps. However, if done wrong, the outcome can lead to significant problems that can potentially kill your engine entirely.

Notably, it’s the threading bit, where you thread the spark plug’s firing ends into their respective empty cylinder heads, that poses a significant risk.

Here, if you don’t pay close attention, it’s easy to inadvertently cross-thread a plug so that it seats improperly in a cylinder head.

After some time(let’s say 6 months or so), the improperly-seated plug can easily loosen and pop out, causing a myriad of problems.

Remember that the engine’s cylinder heads tend to be softer than the spark plugs’ firing heads. After all, the former and the latter are made from Nickel alloy and iridium or platinum, respectively.

As you may know, Nickel alloy is generally weaker than iridium or platinum.

Consequently, not only will you experience engine misfires, but you’ll also have a severely destroyed cylinder head socket. Fixing the head socket may require a re-thread, which can mean disassembling the top half of your car’s engine.


Owning a car comes with incurring regular maintenance and repair costs. Fortunately, handling minor maintenance and repairs such as replacing worn spark plugs on your own can be a great way to save on those mechanic bills.

Speaking of which, spark plugs play a key role in ensuring your car starts properly. Though these crucial components of your car’s internal combustion system are built to last, it’s advisable that you change them every 60,000—80,000 miles or so, depending on the car.

Speaking of which, if you’ve just changed your plugs, it’s recommended to do a few things before getting your car on the road. This will ensure that you get the most functionality out of your new plugs.

Apart from that, it will also help ensure that you’ve installed the new plugs properly, keeping potentially costly problems at bay.

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