BMW DIY Video – Spark Plug And Coil Replacement, 4-Valve Engines (V8 and 6-Cylinder)
All 6-cylinder and V8 models, 1992 and later (except 535i and 735i), use a Direct Ignition system (also known as “coil-on-plug”). In this system, individual ignition coils for each spark plug are mounted directly above the plugs. As a result, BMW models with Direct Ignition do not have the distributor cap, rotor and spark plug wires that many of us grew up with.
BMW models with “Direct Ignition” use two basic designs for the coils; “bolt-in” and “pencil style”. This DIY covers the bolt-in coils (bolt-in coils will have either square or round coil upper sections). See our DIY video on the pencil-style coils for later models that use this design. CLICK HERE for pencil-style coil DIY video.
Follow along with our DIY video (below) as we show you how to replace the spark plugs, boots and/or coils on a 2001 3.0 Z3. This is the M54 6-cylinder engine, with the bolt-in coils. The earlier M50, M52, S50, S52 and the later M56 and S54 6-cylinder as well as theV8 models, will be similar. Later models will use the pencil-style coils. In this case, see the DIY video referenced above.
On models with Direct Ignition systems, BMW recommends 100,000 miles before changing the spark plugs. We believe this is part of an industry-wide effort by car manufacturers to make their “cost of ownership” figures look better to potential buyers and consumer reporting agencies. All this may mislead one into assuming that no standard “tune-up” maintenance is required on these engines. This is simply not the case. Now that these Direct Ignition systems have been out in the real world for several years, we are seeing specific areas where ignition tune-up maintenance is needed. We are finding that, for better fuel mileage, better performance and longer catalytic converter life, it’s a good idea to change the spark plugs sooner than the recommended 100,000 miles. Additionally, the rubber boots that connect the spark plugs to the coils are deteriorating. This allows sparks to arc to the spark plug tube walls, creating misfires. One of the most common “check engine” fault codes Otto is asked about is “Random Misfire.” When this code is generated, a common cause is faulty spark plug connector boots.
Another cause for the “Random Misfire” fault code is a leaking valve cover gasket. If the rubber seals for the spark plug tubes begin to leak, engine oil can collect in the tubes. This creates the possibility of a misfire due to the spark arcing from the connector boot. Given these reports of failures and poor performance, we are recommending a simple tune-up on Direct Ignition systems between 60,000 and 75,000 miles. Performing this tune-up is relatively easy and straightforward, and the cost ranges from $100 to $250, depending on the number of cylinders, etc.