Spark Plugs

If batteries weren’t a part of an engine bay, spark plugs would have been the most commonly known engine part of a car. That is because every time your car refused to start, it was probably because you forgot to put in the key, or your spark plugs, sparked enough.   

Humanity has been using spark plugs for over 100 years now. They are the most basic of a component yet, they serve a very important purpose. After all, they are the reason why every time you press the ignition, your baby fires right up!   

So, what is this spark plug I keep talking about, how does it work, why do we need it, and most of all when do we need it and how to replace it? This post is going to answer all of these questions for you.  

Spark plug and its functionality

Spark plugs are basically circuit with an arc that create sparks. They do so with the help of electricity from car batteries. When you press ignition, electric current from your battery reaches the induction coil of the spark plug which raises the voltage to 20,000-25,000 volts. This causes the electricity to jump from the coil to the ground electrode creating a spark. But, why is this so necessary? 

Well, in order to start an engine, you need to have combustion. Combustion of air/fuel mixes, compressed by a piston, inside a chamber called a cylinder. In order to ignite the air-fuel mixture, a spark plug is introduced. A spark plug simply creates an electric spark that ignites the compressed air/fuel mix and hence combustion happens. 

This is what we call an ignition and since the combustion is happening internally, the engine is called an internal combustion engine. Once combustion is complete, the blast forces the piston down which then creates a vacuum in the cylinder. The intake valve then again fuel in air/fuel mix which is again compressed and ignited, and hence a cycle is achieved. This is how your baby “fires up!”.  

So, now we know the importance of a spark plug and why it is needed. But why do we need to replace it? After all, they are just creating sparks, right?
 

Replacing spark plugs 

It is true that spark plugs just create sparks that help in the ignition and combustion. However, it is not just once or twice, a spark plug sparks about 4000 times/minute at 4000 rpm for a twin stroke engine. That is about 66 sparks/second. These numbers do vary depending on the type of engine and the speed of the car, but the work is still the same.

So even though they just create sparks, with age, their sharp edges get worn out and a greater amount of voltage is required to bridge the gap to create sparks. This not only cost efficiency, but it also results in a lack of performance, burning off excess fuel and causing ignition problems.  

As spark plugs are also designed to be extremely durable, their maintenance mostly goes unnoticed until the problem starts arising. To prevent that from happening you must know when to change your spark plug.

How often does my BMW needs new spark plugs?

Spark plugs are designed to last the longest. In general, a spark plug can last up to 80,000 miles without causing trouble. However, it also depends on the type of spark plug, and the type of engine your BMW has.  

In most modern BMWs, manufactured after 2010 with the N20 or N55 engines, it is required to change spark plugs every 60,000 miles. For BMWs with V8, V10, or N54 or N63 engines, 37000 miles are the threshold before getting new spark plugs. As for BMW models between 1999 to 2009, sparks plugs are replaced at 80,000 miles due to their platinum and iridium tipped plugs.  

To get a more accurate understanding, you can either check the owner’s manual or simply contact BMW of Reading.   

Now, that we have figured out the life of a spark plug, another question arises. Why do they have a different life span?

Types of spark plugs for BMW

Well, Spark plugs are made up of different components that use different materials. However, the type of spark plugs generally depends on the material used for making the core electrode. These materials vary depending on the budget and requirements of a manufacturer. Which also affects the life of a spark plug.   

In general, there are three types of spark plugs-  

Copper Spark Plug – 

Copper Spark Plugs are the most common type of spark plugs in the market. These spark plugs have a solid copper core center electrode covered with nickel alloy for better heat resistance. They have a life span of 20,000 miles. Since Copper is a good conductor of heat and electricity, they are used in high-performance cars with a turbocharged engine having high compression ratios.  

Platinum Spark Plug –

Just like copper spark plugs, Platinum Spark Plugs are also made up of Platinum core. However, unlike copper, Platinum are hard metals with a high melting point. Due to which platinum burns hotter and offer cleaner combustion, boosting engine performance. This toughness also makes platinum spark plugs 4 times more durable than copper pushing its life span to 80,000 miles. 

The Platinum Spark plugs are of two types. 

  • Single Platinum Spark plug- These plugs are similar to copper spark plugs in terms of design with a platinum disc welded to its central electrode. These are also the spark plugs used in most BMW models. 
  • Double Platinum Spark plug- Compared to single platinum, the double-platinum spark plug has an additional platinum disc welded to the tip of its side electrode. This helps the Double Platinum Spark to reduce spark waste and provide better efficiency. 
?Iridium Spark Plug – Iridium spark plugs are the best type of spark plugs on the market. They have a wire center electrode and have a melting point of 2446° C. This not only makes them extremely durable but also provides way cleaner and efficient combustion then platinum spark plugs. These spark plugs have better efficiency and offer greater fuel economy and engine performance.
The type of spark plug needed for your BMW is mentioned in the owner’s manual. If still not sure, you can contact BMW of Reading to find out.   

 Now that we have learned all about spark plugs, it’s now time to learn how to change spark plugs.

How to buy and replace spark plugs in BMW?

Replacing spark plugs is a straightforward simple process. It’s just a bit lengthy. But hey, I won’t complain about saving $150- $300. So, let’s get started. 

First, we will need some tools and materials. 

    • Torque Wrench
    • Gap Gauge
    • Socket/Ratchet set
    • Swivel socket
    • Spark Plug wire puller
    • Needle-nose Pliers
    • Rags
    • Anti-seize compound

Once you have got the tools, it's time to “pop the hood”. The very first thing we need to do is get to the spark plug. To do so, you will first have to remove the cabin air filter and then the engine cover. Here is how you do it.     

Note- The following images are from a 2006 BMW 33xi. 

  1. Start by removing the cabin air filter. It is secured by 6-screws (8 mm). Use the image below as a reference. 

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  1. Once that’s removed, remove the side plastic covers on both sides as shown in the image. 

 

 

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  1. After removing the covers, unlatch the two connectors by just moving upwards or in a clockwise direction.  

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  1. Now, simply pull back the black bar. It will be connected to three more hinges, just unlatch them, and it should easily come out. 

 

 

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  1. Then remove the 8 mm screw on either side.  

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  1. Now lift the cover-up and keep it aside. After that also remove your engine cover. As you do that, your ignition coil (coil pack) should be visible. 

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  1. As you pull up on the clip of the coil pack, it will release from the harness automatically. 

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  1. After releasing the clip, simply pull or use a socket extension to gently twist and pull out the coil pack.

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  1. Now use a torque wrench with a swivel socket (Drive 6 Point 5/8”) to unscrew the spark plug. Once that is done its time to put in a new one. 

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  1. 10. If you have a pre-gapped plug i.e. a plug with a gap between both its electrode you can screw it right in. If not, use the gap gauge to create a gap.  

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  1. Once you have put in the new spark plug. Use the torque wrench tighten it.  

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  1. 12. Then, just insert the new coil pack and harness it as before. Now, repeat the same process for the remaining spark plugs and coil packs. 

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  1. After you are done replacing the spark plugs, put the engine cover back on and screw everything back in place.

And that concludes with the change of spark plug. However, don’t forget to start the engine and check if everything is working fine. In general, changing spark plugs won’t take much more than an hour. But if you are too busy to do it, there is always a dealership. Whichever you choose, replacing your spark plugs from time to time is a necessary part of your BMW maintenance.  

 

 

 

 
 
Categories: Service, Parts