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BMW 335i: Plug & Coil Install

At, everyone knows we’ve got some of the best prices around, and those savings can help offset the cost in labor for having your ordered parts installed. However, some parts can be fairly simple to install. Therefore, why not learn how to install some of these items and save as much cash as you can?

Depending on the application, most cars require spark plug changes anywhere between 25,000 and 50,000 miles, while some of the more heavily supercharged or turbocharged performance cars may need them changed much sooner than that to always run at an optimum level.

On the flip side, more and more cars are using long life iridium/platinum plugs which have much longer intervals. In fact, several Mercedes models - including the 5.5- and 6.0-liter V12 twin turbo Mercedes engines found in the S600 and AMG S65/SL65 chassis call for up to 100,000-mile intervals! So, make sure to check your owner’s manual.

For those of you driving turbocharged cars - especially those with aftermarket software upgrades to allow more boost - you’re probably going to be changing plugs more frequently. The BMW 335i is one of those turbocharged cars that frequently get boost upgrades.

The 2007-2009 E90/E92 BMW 335i is powered by the twin turbocharged inline-six N54 motor, which is rated at 300 bhp. Although it is believed that that number is very conservative, due to how well they dyno test to the wheels (about 280-290 in stock form), thousands of enthusiasts are powering around with updated software, putting their cars at well over 370 bhp, and with much greater gains down low in torque.

This bump in power wears plugs down sooner, which takes its toll on the ignition system until it can’t keep up any longer. With the N54 motor (which is also found in the 135 and 535, depending on the year), several enthusiasts have had issues with bad plugs or worn coil plugs, even on stock cars. With modified cars, this issue is exacerbated. We’re happy to announce that NGK has just released its cost-effective replacement coils for these cars in 2017.

We will be installing a fresh set of factory-replacement spark plugs as well as NGK's new replacement ignition coils. Due to the plugs’ thinner design, we’ll need a narrow 12-point 14mm or 9/16" spark plug socket.

Unlike a conventional, single electrode unit, the OE plugs for this model BMW have three ground electrodes with a very narrow gap.

These are the NGK coils for the BMW N54 engine that were just released in 2017. They are NGK part# U5055, US stock# 48705.

BMW 335i Spark Plugs and Ignition CoilsBMW 335i OE Spark PlugsNGK Ignition Coils U5055


Here's what we're working on: a BMW N54 3.0-liter twin turbo engine. While it is a little different than the N55 twin-scroll single turbo found in the 2010+, the procedure should be somewhat similar. For the latter you’ll just have to remove the factory airbox as well.

BMW 335i Engine Bay














NOTE: It is always a good idea to DISCONNECT THE BATTERY before working on anything fuel- or ignition-related, so please start by doing that now.


We’ll want to remove the engine cover on the passenger side, but in order to access its rear two screws we have to start with removal of the cowl. Use an 8mm socket to remove the cowl’s screws. You will see six. See Image A

There are eight screws total securing the engine cowl, however. In order to access the last two screws you’ll have to remove the brake reservoir cover on the driver side… See Image B

…along with the ECU cover on the passenger side. These covers just pop right off after releasing the tabs with a careful pull-and-wiggle technique. See Image C

Accessing BMW 335i Engine BayRemoving BMW 335i Brake ReservoirRemoving BMW 335i ECU Cover


You’ll also notice that on both sides are factory plugs that need to be carefully undone before the cowl is released. See Image D

Using a screwdriver we can carefully undo the clips that hold the wiring harness in place. See Image E

With all eight screws undone and the wiring harness released, the cowl can be put aside. If you flip it upside down you’ll have full access to the cabin filter, which is a good, while-you’re-at-it upgrade as well. See Image F

Disconnect BMW 335i Sensor ConnectionsRemove BMW 335i Retaining ClipsBMW 335i Cabin Air Filter Access


Keep the eight screws handy, since you’ll be using them again to reinstall the cowl. See Image G

With the cowl out of the way, we’ve got access to the back two screws that hold the engine cover on. Without the cowl off it would be very difficult to remove the engine cover, let alone have access to the coils on cylinders 5-6. See Image H

With access to all four engine-cover screws, we are ready to remove it. They take a 5mm Allen head. See Image I

Cowl Screws in a Magnetic Parts TrayBMW 335i Engine CoverRemove BMW 335i Engine Cover


With the engine cover off, we’ve got access to the coils. Notice one coil for each cylinder. This setup is called “coil-over-plug.” See Image J

To remove each coil, all we have to do is flip the tab up, which disconnects the wiring, and pull. On some cars you may have to give each coil a good tug. Use thick gloves to protect your finger. See Image K

Once the coils are removed, the spark plugs will be exposed. It’s now time to grab the plug socket. See Image L

BMW 335i Coil Over Plug SetupRemove Ignition CoilsBMW 335i Spark Plug Well


A conventional spark plug socket will not work on these plugs. You’ll need a THIN-walled (because the plug galleys are very tight) 12pt 9/16" or 14mm socket. See Image M

Using a 3/8 socket ratchet wrench and extension, remove each spark plug. See Image N

With the plugs out, inspect each one. You’ll want to see a tan or light grey hue on each one, indicating normal combustion. When reinstalling each plug, make them snug but don’t over-tighten because they are going onto an aluminum cylinder head. You’ll feel the sudden resistance when the washer is fully crushed. See Image O

Thin-Walled Spark Plug SocketRemoving Spark Plugs BMW 335iInspect Spark Plugs for Normal Wear


To reinstall everything again simply reverse the steps and your BMW should be a happy camper once again! This car in particular was no exception - it picked up a tenth of a second in a third-gear, 30-100 MPH pull with its new OE plugs and NGK coils!  (8.9 seconds vs 9.0 seconds with its factory setup).

BMW N54 3.0L Twin Turbo