This article covers replacing both the spark plugs and ignition coils (also known as a “tune up”) in a BMW F30 3 series vehicle with the N20 engine. The N20 engine is also used in a wide range of other BMW models including the 1,2,4,5,X1,X2,X3,X4 and Z4 series cars and SUVs. This article can be applied to any vehicle with the N20 engine with minor modifications to the repair steps.
A BMW F30 spark plug replacement can help cure a rough idle and poor performance in your N20 turbocharged engine.
In 2011 BMW introduced the N20 four cylinder turbocharged engine into its model line up. It was to be the successor to the venerable line of normally aspirated inline 6 cylinder engines that had powered most of BMW’s vehicles since the late 1980s. The inline turbocharged four cylinder N20 produces the same horsepower and torque as the larger six cylinder engines in a more fuel and weight efficient package.
There have been reports from BMW F30 3 series owners of a noticeable decrease in performance around 40-50,000 miles including poor acceleration, rough idle, engine stalls, and fluctuating low speed RPMs (like when “rolling” to a stop with the foot off of the accelerator). Many of these issues are directly attributable to failing spark plugs and ignition coils in their N20 engines.
The BMW Service and Warranty Book for the F30 3 series recommends changing the spark plugs in your 2012-2019 3 series every 60,000 miles. Based on information we have accumulated from F30 owners, we feel this is too long a period. The BMW Repair Guide recommends replacing the spark plugs in your N20 engine every 40,000 miles to keep your vehicle performing normally. There are no recommendations on ignition coil replacement in the service and warranty book, but we feel it is good practice to always change them out with the spark plugs.
A BMW F30 spark plug and ignition coil replacement is a straightforward repair that can be completed in about an hour. It involves replacing the ignition coils and spark plugs in the four cylinders. The good news is the cylinders in the N20 engine are easily accessible – a minimal amount of engine parts have to be removed to complete this repair. Doing your own BMW F30 spark plug replacement is a big money saver as well…it can be performed in your garage for a fraction of the cost charged by the dealership or your local repair shop.
1. Spark plugs (required) – Always use superior OE quality spark plugs in your high performance BMW N20 engine. Never use “cheap” aftermarket spark plugs in the N20 engine…they do not perform at the same level as OE plugs and have a high failure rate. We give you several excellent choices below based on your brand preference and budget.
2. Ignition coils (required) – Like the spark plugs, only use superior quality ignition coils specifically recommended for use in your F30 3 series vehicle. The following are all excellent choices from upper tier manufacturers.
3. Air filter (optional) – Now is a great time to replace your air filter element. Feed your new spark plugs and ignition coils clean fresh air with an inexpensive air filter! Please see our article BMW F30 Air Filter Replacement if you need help installing it.
Preparing the engine so the N20 spark plugs and ignition coils can be accessed is a relatively easy procedure taking less than 15 minutes. Please note that it is important that the strut braces are loosened (step 9) to create enough space to get the upper partition out without breaking it.
- Always disconnect the negative terminal of your vehicle’s battery before starting this repair. Since you will be working in the engine compartment with metal tools near a live positive terminal, failure to disconnect the battery could create a short circuit causing catastrophic damage to sensitive electronics.
- Begin by removing the engine cover. It is held in place by three rubber mounts. Simply pull it free from its mounting bracket and remove it from the engine compartment.
- Remove the sound insulation from the top of the engine.
- Use a 10mm nut driver to release the three plastic locking mechanisms on the right apron. Grasp the apron and remove it from the engine compartment.
- Repeat the same procedure on the right apron.
- In order to gain access to the rear number 4 cylinder, the top equipment partition must be removed. Begin by removing the seven 10mm bolts anchoring the partition to the body of the car.
- Remove the rubber engine sealing gasket from the partition.
- Remove the wiring harness from the sealing gasket. Remove the sealing gasket from the vehicle.
- Use an E18 external torx socket to remove the two strut brace bolts. You will need to remove these bolts so the strut braces can be raised just enough to allow enough room to remove and reinstall the top partition.
- Lift the strut braces and maneuver the top partition underneath them. Remove the partition from the vehicle.
- You now have clear access to all four cylinders.
The four BMW N20 spark plugs and ignition coils are very easily accessed on the right side of the engine. The BMW Repair Guide strongly discourages the use dielectric grease on the ignition coils during reassembly – dielectric grease can cause the coils to slip off of the spark plugs causing misfires.
- Starting with cylinder number one, release the plastic locking clip on the ignition coil and remove its plug.
- Pull the ignition coil off of the spark plug. Use a socket extension to assist pulling it out if necessary.
- Using a 14mm thin wall spark plug socket, remove the spark plug from the cylinder.
- Apply a small amount of anti seize lubricant to the new spark plug.
- Install the new spark plug and hand tighten.
- Using a torque wrench, torque the spark plug to 25 Nm (18 ft-lb).
- Insert a new ignition coil into the spark plug tube and install the electrical plug. Make sure the plug is pushed in snugly as far as it will go into the ignition coil. DO NOT apply dielectric grease to the ignition coil…this will cause the coil to slip off of the spark plug causing a misfire.
- Push the coil firmly down onto the spark plug using the palm of your hand.
- Repeat the above steps on the last three coils.
- Before reassembling the vehicle, start the engine and check to make sure it is running smoothly.
- Reinstall the top partition and its seven mounting bolts.
- Reinstall the strut brace bolts and torque to 25 Nm (18 ft-lb).
- Reinstall the engine sealing gasket and its wiring harness. Make sure the gasket is correctly seated on the top partition to avoid and water and debris from entering the engine.
- Install the aprons making sure they are securely snapped in and the locking mechanisms are secure.
- Reinstall the sound insulation and the engine cover.