BMW Spark Plug Replacement Guide
In this guide, you will find step-by-step instructions on how to replace BMW spark plugs. This guide was written for six-cylinder 5-Series BMW. Owners of BMW 1 3 5 6 7 X1 X3 X5 series should find some of this information helpful since BMW uses the same engine accross many models.
What will you need
- Set of new BMW spark plugs
- New Ignition coils (optional)
- Connector rubber boots (when applicable, for engines up to 2004.)
- 14mm or 5/8“ deep hex socket (for all engines except direct injection)
- 14mm thin wall bi-hex socket with wobble function (for direct injection engines)
- 3/8“ long extension
- 3/8" Ratchet
- 3/8" Torque wrench
- 3/8“ or 9mm rubber hose, 1/2 feet long (highly recommended)
- 8mm socket
- 10mm socket
- Phillips and flathead screwdrivers
- Silicon grease (recommended for connector rubber boots)
- Turn the ignition OFF and open the hood.
- Remove the drain tray that is installed below the windshield to gain access to the spark plugs at the rear part of the engine. On some models, strut brace is installed over the engine. It can be removed to gain better access, but it is not necessary.
- Remove the engine cover. If it is held in place with screws, unscrew them. If there are no screws visible, just pull the cover off.
- The ignition coil is connector is secured in position by a retaining clip. Carefully unlock the retaining clip. Unplug the ignition coil wiring harness.
- Pull the ignition coil out. If it is stuck, do not use excessive force. You might break it, or the silicon insulator might come of. Wiggle it a bit and twist it back and forth, while pulling out at the same time, until it 'pops-out'.
- Older engines have ignition coils with detachable connector rubber boots. If your engine has these, it is likely that they will detach from the ignition coil when you pull. You will need to pull them out separately.
- If you are reusing ignition coils, inspect them for cracks or contamination. If you spot any of these, do not reuse them.
- Visually inspect the spark plug hole for debris or oil. If there is any, clean it before taking the spark plug out. Take extra caution, as any debris left might fall into the cylinder when the spark plug is removed.
- Using an appropriate socket, extension and ratchet, undo the spark plug and pull it carefully out of the plug hole.
- Visually inspect the spark plug. It can tell you a lot about the state of the engine and that cylinder in particular.
- Push the upper side of the spark plug into the 3/8" rubber hose. Using 3/8" rubber hose as a hand tool, screw spark plug hand-tight into cylinder head plug thread as far as it will go.
- Tighten spark plugs to a specified torque, using a torque wrench, extension, and appropriate socket.
- On engines that have ignition coils with detachable connector rubber boots, renew the boots. Apply a small amount of silicone grease on the inner spark plug side of the boot before reinstalling.
- Reinstall ignition coil assembly. Push it onto the spark plug until you hear a 'pop'.
- Connect the wiring harness to the ignition coil and lock the retaining clips. Double check the connector for looseness. Reinstall engine cover, scuttle drain and any eventual other parts in reverse order to removal
- Start your BMW engine and observe how it operates. Check fluid level if necessary.
- Traces of engine oil on the ignition coil boot indicates leaking valve cover (camcover) gasket. As oil is very aggressive on silicon boot insulation, so camcover seal must be renewed before reinstalling ignition coils.
- Spark plug holes are deep, and usually under an angle. Access to some parts of the engine can be limited. This means that you can easily cross-thread the new spark plugs while installing it. To prevent this, use a rubber hose as a flexible tool that will allow you to safely install the spark plug. This way, if plug starts to cross-thread, rubber hose will slip.
Symptoms of Bad Spark Plug
What you may notice if your BMW spark plugs are worn out or not replaced at the recommended interval.
- Rough idle
- Hard starting
- Engine judder (misfire)
- Power loss
- 'Check engine' light
- High fuel consumption
It is not necessary to change ignition coils every time you change the spark plugs. Visually check the body, connector and insulation for cracks and traces of contamination. If in any doubt, it is better to replace them with new one. They can fail without any prior warning signs. And they are not too expensive.
Changing spark plugs and ignition coils on most BMW engines is quite easy and straightforward. All you need is a basic set of tools, and some elbow grease. This is a great job for a novice DIY-er looking to get some experience.
Spark Plug Replacement Interval (Schedule)
Spark plugs and ignition coils are one of the key engine components in your BMW. So you really need to make sure that they are in good shape.
Usual intervals for preventive spark plug and ignition coil replacement are:
- 60.000 miles for naturally aspirated engines before 1999
- 100.000 miles for newer naturally aspirated engines
- 40.000 miles for all turbocharged engines
Yet, it is possible to have problems with spark plugs before you reach this interval. This can be caused by poor quality fuel, high oil consumption or fuel injection system related problems. Also, ignition coils can fail as a result of damage or deterioration.
Spark Plug Socket Size
On most BMW engines you can use 14mm hex deep socket, or 5/8 deep socket. This are a part of any good tool set.
However, if you have an engine with direct injection, you will need a Thin wall bi-hex socket with wobble function.
Majority of BMW engine use spark plugs with M14 x 1.25 thread. Typical tightening torque for them is 30Nm.
Always verify the correct spark plug torque for your BMW engine, by calling your local dealer. Your dealer can look up the correct torque if you can provide the VIN number.
BMW Spark Plug Replacement Cost
This is an orientation price guide for parts, per cylinder:
- Spark plug (one piece): $5 – $20
- Ignition coil (one piece): $20 – $50
- Rubber boot (one piece): $5 – $15
Price is per one spark plug or ignition coil. You will need as many spark plugs or igntion coils as the number of cylinder in your BMW. Typically four, six or eight.
Frequently Asked Questions
BMW won't start after spark plug change?
If your BMW cranks and doesn't start, it is possible that either coils or connectors are loose. Spark plugs that are not tightened enough can cause this, as well. Also, incorrect plugs could be a cause, so double check that as well.
If your BMW does not crank, you might have a weak battery.
In addition, use a scan tool to check if there are any errors stored.
What is the average life of BMW spark plugs?
It varies from 60.000 miles on older generations of engines, to 100.000 miles on newer generations of engines. However, on new turbocharged engines spark plugs should be changed every 40.000 miles. Poor quality fuel, oil consumption or problems with fuel injection system can shorten spark plug lifespan.
Recommended BMW spark plug gap?
Spark plugs for your BMW come with a preset gap. So there is no need for adjusting the gap. This goes whether you buy OEM spark plugs from your BMW dealer, or aftermarket ones.
What brand are BMW spark plugs?
OEM spark plugs are a good choice for factory tuned BMW. They are are tailored exactly for your engine type, and not expensive, either. Aftermarket brands, such as NGK, Bosch or Denso can also be used. In that case, make sure that you have an exact type for your engine.