This guide was written for a six-cylinder 5-Series BMW. The BMW 1, 3, 5, 6, 7, X1, X3, and X5 series owners should find this information helpful since BMW uses the same engine across many models.
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 on
- High fuel consumption
What will you need
- 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)
How to Change BMW Spark Plugs
- Turn the ignition OFF and open the hood.
- Remove the drain tray installed below the windshield to gain access to the spark plugs at the rear part of the engine. On some models, a 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, pull the cover off.
- The ignition coil is a connector 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 off. 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, they will likely 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 plughole.
- 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 a 3/8" rubber hose as a hand tool, screw sparks 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.
- Reset the spark plug reminder via the instrument cluster.
- Traces of engine oil on the ignition coil boot indicate a leaking valve cover (cam cover) gasket. As oil is very aggressive on silicon boot insulation, so cam cover 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 them. To prevent this, use a rubber hose as a flexible tool that will allow you to install the spark plug safely. This way, if the plug starts to cross-thread, the rubber hose will slip.
Recommended BMW Spark Plug Replacement Interval
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.
What size are BMW Spark Plugs?
On most BMW engines, you can use a 14mm hex deep socket or 5/8 deep socket.
However, if you have an engine with direct injection, you will need a thin wall bi-hex socket with a wobble function.
Recommended BMW Spark Plug Torque
The majority of BMW engines use spark plugs with M14 x 1.25 threads. The recommended tightening torque for most BMW spark plugs 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.
Price is per one spark plug or ignition coil. You will need as many spark plugs or ignition coils as the number of a 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, either coils or connectors may be 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.
Also, 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 systems 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 to adjust the gap. This goes whether you buy OEM spark plugs from your BMW dealer or aftermarket ones.
What are the best BMW spark plugs?
OEM spark plugs are a good choice for factory-tuned BMW. They 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.
It is unnecessary 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 a 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 easy and straightforward. All you need is a basic set of tools and some elbow grease. This is a great job for a novice DIYer looking to get some experience.