Reignite the Fire – Spark Plug Replacement

Repetitive movement is weary but easy to contend

Perhaps the most common engine component recognizes by everyone that has a driver’s license is the spark plug. This small skinny silver and white looking thing performs its duty up to thousands of times a minute without asking much for return. The repetitive movements do eventually wear it out. When it runs out of steam (weak spark) the fire diminishes. A set of new spark plugs will reignite that fire within.

Depending on the type of the spark plugs and the vintage of your, spark plug replacement interval can range from 15,000 to 100,000 miles. The older carbureted engine using copper plugs requires the most frequent replacement due to the imprecise nature of the fueling system, and the wearing rate of the copper electrodes.

In the SX4, Suzuki recommends 60,000-mile interval on the iridium plugs. We were a bit skeptical on that as our experience tells us that the recommended replacement interval on iridium plugs on most cars are 100,000 miles. But we aren’t going to second guess Suzuki’s recommendation knowing their motorcycle history in building great engines.

As part of the big 60K celebration, we changed the factory plugs. We selected NGK Laser Iridium (Part# IFR5J11-7418). It is the direct OEM replacement in both heat range and center electrode material. We have been big fans of NGK plugs for as far back as we started to experimenting different type of plugs from Splitfire to Bosch in our Nissans and combing the experience from an older generation of wrenching on two-stroke motorcycle and Datsun engines. The general rule of thumb is to stick with the OEM plugs even little some mild modifications. Our past engines ran the best with OEM plugs and all were made by NGK.

Function of Spark Plug

The three fundamental elements for a spark-ignited engine to work are combination of fuel-and-air mixture, compression, and spark all happening in a precise synchronized way. The spark plugs as part of the ignition system are the heart of this process.

The only purpose of the spark plug is to create an electrical arc (spark) between the central and lateral electrodes from the high-voltage electric current from the ignition coil. The spark will ignite the highly compressed fuel-and-air mixture to generate the power stroke.

The spark plugs are situated in the harshest part of the engine. It is constantly exposed in extremely high temperature, chemicals in fuel and engine oil, and carrying up to 45,000 volt. The plugs are subjected to various kinds of contaminations, and corrosions over time particularly on the electrodes.

Worn out plugs causes rough idling, poor performance, excessive fuel consumption, and elevates emission due to incomplete combustion.

Changing the plugs periodically is the best method to keep engine efficient at its optimal condition. It is our recommendation to replace the 100,000 mile spark plugs earlier. There are some cases that the carbon deposit on the plug or somethings the threads can seize in the cylinder head making the removal problematic.

How to Do It

Spark plug replacement, like changing oil, is the most basic wrenching skill any driver should acquire. It is a known fact that some front wheel drive V6 engines can be a pain to do. That’s one of the reasons why we are never a big fan of V6 FWD. On our SX4, or good majority (except Nissan Versa) of 4-cylinder FWD cars, plugs are simple to replace.

Tools Needed:

  • Spark Plug Socket
  • 10mm Socket
  • 3/8” Drive Ratchet
  • 3/8” Locking Extension Bar
  • Anti-Seize Lubricant
  • Spark Plug Gap Tool – Wire Type

Time spent: 30 minutes

Cost: $9.40 each on Total comes to $40.85 for a set of four including shipping.

Here is the Process


Use the information here at your own risk. We take no responsibility and will not be held accountable for any safety issues, or any problems whatsoever.If you are not mechanically talented or never open a hood before, please do not try this on your own. Seek help.

1. With the engine at room temperature. Remove the air intake box.

2. Disconnect the electrical wires at the ignition coils

3. Temporary route the wiring away from work area

4. Remove the ignition coils by undoing the mounting bolts and pulling them up vertically one by one

5. Undo spark plugs from cylinder head using spark plug socket with locking extension bar and ratchet. Turn counter-clockwise to loosen. Normal spark plugs are easy to break loose, and smooth to turn. If not, spray the thread with small amount of penetrating/lubricating oil and allow time to soak. Improper installation, excessive carbon deposit, and a plug left untouched for too long can increase difficulty in removal. Do not force it to avoid very costly damage to threads on cylinder, particularly aluminum ones.

6. Check and adjust the gaps on the new spark plugs using gap tool. No adjustment was needed on our NGKs.

7. Apply anti-seize lubricant to the thread of the spark plugs to make future removal easier.

8. Install the new plugs using socket and locking extension. Be careful with the first few threads. Make sure the plug is centered with the cylinder head before tightening. Hand-tighten all plugs by twisting the locking extension with your fingers until plugs are properly seated.

9. Use ratchet to tighten plugs to spec; about ¼ turn. DO NOT OVER TORQUE. It takes a lot less than you think to reach proper torque.

10. Reinstall ignition coils. Reconnect wires. Reinstall air intake box.

11. Remove all tools and foreign objects in engine bay. She should fire right up and purr with smoothness.

Old Plug Examination

Before tossing out the old plugs to the trash, let’s do an educated examination. The color on the tips of the plugs tells the combustion efficiency, and overall health of the engine.

In the old carbureted days, combustion efficiencies are evaluated by removing the plugs to check on the recently tuned carburetor by examining the color of the porcelain around the electrodes. Ash white indicates a lean condition (too much air, too less fuel). Grimy black is too rich (too little air, too much fuel). The optimal tune is when the porcelain color is in between the two, or grey to brownish.

Nowadays, the ignition, fuel/air mixture and timing have gotten stronger and more sophisticated. Majority of the plugs we remove are in optimal color. However, you can still check the overall health of the engine from the plugs.

Oily residual means internal oil leak from the piston rings, cylinder walls, and valve guides. Deposits on the firing end are influenced by oil leakage and poor fuel quality. Heavy detonation can break the porcelain surrounding the electrode.

When examined individually, the plug will indicate the condition of that specific cylinder. However, when the entire set of plugs is compared side-by-side, it identifies if there’s any variation between the cylinders. Ideally, all plugs should have the same coloring which suggesting all cylinders are performing evenly.

Typically wear on the plug would round off the sharp edges of the electrodes. Gap is generally increased due to this loss of material. Our old plugs, as shown in the picture above, showed some initial stage of the wearing. They probably had another 10,000 miles left in them but engine efficiency would rapidly decrease. Therefore, Suzuki’s recommendation is right on the money.


Engine response to throttle input is snappier. Under high load, engine pickup is crisper. Our SX4 feels like brand new once again.

Lamzgarage Health Tip

An efficient engine reduces air pollution and fuel consumption that tree huggers will appreciate. LZG