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Have you been experiencing the symptoms of failing spark plugs without even realizing it? Hard starting, poor fuel economy, and a noticeable drop in power are just a few of many. 

In this guide, Gareth Foley, our BMW Catalog Manager, tears into an N55 and and teaches us a few of his tips and tricks when replacing the spark plugs. 

 

BMW models and years with the N55 engine:

There is a wide range of models and years that shipped with the N55 engine. This DIY will apply to all of them.

  • 2008-2017 BMW X6
  • 2011-2017 BMW 535i GT
  • 2010-2012 BMW 550i GT
  • 2011-2017 BMW X3
  • 2009-2012 BMW 750i
  • 2012 BMW 650i
  • 2009-2012 BMW 750Li
  • 2012-2018 BMW 640i
  • 2010-2012 BMW 750i xDrive
  • 2012 BMW 650i xDrive
  • 2010-2012 BMW 750Li xDrive
  • 2013-2018 BMW 640i Gran Coupe
  • 2010-2012 BMW 550i GT
  • 2013-2015 BMW X1
  • 2010-2017 BMW X5
  • 2013 BMW 135is
  • 2013-2015 BMW 740Li
  • 2013-2015 BMW 740i
  • 2011-2015 BMW 335i
  • 2012-2016 BMW ActiveHybrid 5
  • 2011-2015 BMW 335i xDrive
  • 2013-2015 BMW ActiveHybrid 3
  • 2011-2016 BMW 535i
  • 2013-2015 BMW ActiveHybrid 7
  • 2015-2018 BMW 640i xDrive
  • 2011-2013 BMW 550i
  • 2014-2018 BMW 640i xDrive Gran Coupe
  • 2011-2017 BMW 535i GT
  • 2014-2016 BMW 435i
  • 2011-2012 BMW Alpina B7
  • 2014-2016 BMW 435i xDrive
  • 2011-2012 BMW Alpina B7L
  • 2014-2016 BMW 335i GT xDrive
  • 2011-2013 BMW 135i
  • 2014-2016 BMW M235i
  • 2011-2012 BMW Alpina B7 xDrive
  • 2015-2016 BMW 435i Gran Coupe
  • 2011-2012 BMW Alpina B7L xDrive
  • 2015-2016 BMW 435i xDrive Gran Coupe
  • 2011-2016 BMW 535i xDrive
  • 2015-2016 BMW M235i xDrive
  • 2015-2018 BMW X4
  • 2011-2013 BMW 550i xDrive
  • 2016-2018 BMW M2

 

What are the symptoms of bad spark plugs on a BMW N55?

When spark plugs begin to fail, they can't properly ignite the fuel in your cylinders properly. Due to this, it can cause a multitude of symptoms.  

  • Rough Idle
    • A healthy engine should idle smoothly at a consistent RPM. If you begin noticing harsh vibrations, surges or drops in RPM, it's a good sign that one or more of your spark plugs are failing. This happens due to the ECU attempting to compensate for the lack of spark. 
  • Poor Fuel Economy
    • Have you noticed a drop in your fuel economy from when you first got your car? As plugs age, they lose their effectiveness to ignite the fuel, causing your car not to burn it as efficiently. 
  • Poor Acceleration
    • Is your car feeling slower than it once did? It all comes back to how well it's burning the fuel. If it's not being burned as efficiently, your car will not accelerate as quickly. 
  • Smell of Fuel from Exhaust
    • This is directly related to the ones above. If the fuel isn't being burned, it will exit your combustion chamber and be deposited into your exhaust system. There it heats up and smells strongly. 
  • Hard to Start
    • One of the most difficult times for your car to get its fuel and spark correct is during startup. Since spark plugs don't usually fail simultaneously, your car should struggle to start, but eventually, start up. 
  • Engine Misfire
    • Since fuel isn't being ignited, there's a good chance you won't have combustion in the cylinder with the bad spark plug. If this is the case, you will feel and hear a stumbling from the engine. This is usually accompanied by a check engine light/code. 

I wouldn't ignore the signs of faulty spark plugs. There's a possibility that it's something more serious than just your plugs. Checking your plugs is a good first step to determine if it's something worse that needs addressing immediately. 

BMW has a regular service interval of 60,000 miles for the OEM spark plugs. They can fail well before then, or even later, so it's worth checking. Also, inspection of your spark plugs lends insight into the health of your engine. 

 

How long will it take to replace BMW N55 spark plugs?

On a lot of cars and engines, it only takes a few minutes to replace your spark since so much has to come off the engine to get to the plugs on an N55, you can expect it to take you around 2 hours to complete this job. 

 

How much does it cost to replace BMW N55 spark plugs?

If you plan to take your car to the dealer to have this job done, you can expect this to run anywhere from $300 to $500. By purchasing the parts through us and doing this job yourself, you will only pay a fraction of the cost. Plus, when you need to replace them again, you can make use of our Lifetime Replacement Guarantee

 


 

Tools required to replace BMW N55 spark plugs:

 

Parts required to replace BMW N55 spark plugs:

 

Steps required to replace BMW N55 spark plugs:

Step 1: Remove the engine cover and intake

Start by removing the engine cover and the air intake. On this car, there's an aftermarket intake installed. However, removal of the stock airbox is very straightforward. 

You will need a flat head screwdriver to remove the hose clamps and possibly a pick tool to help remove the electrical connector. 

01-bmw-n55-spark-plug-replacement-intake-engine-cover

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03-bmw-n55-spark-plug-replacement-cover-removal

 

Step 2: Remove the inlet pipe

To remove the inlet pipe, you have to remove the connectors from it. Low and to the front, there's an electrical connector. Further back from that, you have one corrugated pipe as well as one vacuum line. The last thing to remove is the hose clamp that is lowest and in toward the front. 

Use care when removing all of these clips. Some of the pipes and the clips themselves become brittle over time and can break very easily. 

There's only one fastener holding on the inlet pipe, and it's a 10mm. Once that's removed, you can simply pop the entire inlet pipe right off. The inlet pipe can become brittle over time, so be cautious not to crack/break it when removing it. 

04-bmw-n55-spark-plug-replacement-inlet-pipe-electrical-connector

05--bmw-n55-spark-plug-replacement-vacuum-pipe-connector

06-bmw-n55-spark-plug-replacement-hose

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08-bmw-n55-spark-plug-replacement-inlet-pipe-screw-10mm

09-bmw-n55-spark-plug-replacement-inlet-pipe-removed

 

Step 3: Remove the ignition coils

Now that the inlet pipe is removed, you have access to the ignition coils. The first step is to remove the connectors. All you have to do is flip up the connector, and it should pull itself right out. 

Once the connector is out of the way, you can pull the ignition coil straight out. It's helpful to use a tool, such as a pick or a screwdriver, through the hole on the top of the coil to have a little more to grab onto. 

10-bmw-n55-spark-plug-replacement-disconnect-ignition-coils

11-bmw-n55-spark-plug-replacement-remove-ignition-coils

 

Step 4: Remove the spark plugs

Removing the spark plugs on your N55 is just as easy as any other car. However, you are going to need a special 14mm 12-point thin-walled socket for this task. The spark plug well on the N55 is extremely narrow, so your typical chrome spark plug sockets will not fit. You are also going to need an extension to reach down that far. 

12-bmw-n55-spark-plug-replacement-remove-spark-plug

 

Step 5: Reverse steps and reinstall 

Once you have the spark plugs out, it's a good time to take a look at the condition of them. This gives helpful insight into how your engine is running⁠—whether that's too lean, too rich, or if oil is making its way onto your plugs. 

After you've inspected them all, you can begin reinstalling. We recommend using a torque wrench to install your new plugs, and the torque spec for those is 23Nm. There is no need to use anti-seize here as the new plugs are plated and will not seize into the head. 

When you get to reinstalling your coil packs, you will notice that there is an indent in the casting on the cylinder head; this is to align the coil pack properly. Once it's aligned, all you have to do is push it down into place.

For the remainder of the reinstallation, you want to follow the steps above in reverse. 

13-bmw-n55-spark-plug-replacement-reinstall-ignition-coil

 

BMW N55 Spark Plug Torque Spec:

  • BMW N55 spark plug torque spec = 23Nm or 17 lb-ft of torque. 

Going any further than this can cause damage to your cylinder head. 


That's it! Your plugs are replaced, and hopefully, your car is running strong once again. If that didn't solve your issues, it might be worth looking into if your symptoms are stemming from your ignition coils, instead.

If you're interested in more DIYs for your BMW, you can visit bmw.fcpeuro.com or subscribe to our YouTube channel. 

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Written by :
Evan Madore

Writer/Editor at FCP Euro and owner of a daily R53 MINI Cooper, a track-built R53 MINI, and a 1997 Dakar Yellow E36 M3 Sedan. ••• Instagram: @evan.madore


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