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Spark Plug, Ignition Wire, Coil Replacement
 
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Pelican Technical Article:

Spark Plug, Ignition Wire, Coil Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$30 to $400

Talent:

***

Tools:

Set of sockets (10mm, 5/8 spark plug socket), flathead screwdriver

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Spark plugs, Ignitions coils, ignition wire set

Hot Tip:

Work with a cool engine.

Performance Gain:

Engine runs well

Complementary Modification:

Replace ignition wires (4-cylinder engine)

The digital motor electronics (DME) engine management systems used in BMW vehicles controls fuel supply, fuel injection, ignition and emissions. In these systems, an electronic microprocessor, the engine control module or ECM, processes a variety of sensor inputs to monitor engine and vehicle conditions. The ECM operates the engine in accordance with driver input. It has self-diagnostic capabilities in accordance with US-mandated on-board diagnostics (OBD-II) standards and stores fault codes known as diagnostic trouble codes or DTCs that can be accessed for troubleshooting purposes.

In the DME system idle speed, idle mixture and ignition timing are not adjustable. OBD-II standards require the engine to operate within extremely tight tolerances maintained by feedback loops in the electronics. These standards as well as upgraded manufacturing materials and techniques allow many automotive components to function well past times and mileages that were considered normal in previous decades. As examples, engine oil and spark plugs are capable of extended life compared to the past.

Replacing the spark plugs on your BMW Z3 is part of routine maintenance. BMW recommends replacing the spark plugs on Z3 models every 100,000 miles and on M Roadster models every 60,000 miles. As mentioned above, with all the major engine and engine management design changes over the years, spark plugs now last up to three times as long as they did in years past.  This is both good and bad. It means you save money and time not having to service them so frequently, but run the risk of a spark plug seizing in the cylinder head. I suggest replacing your spark plugs every three years regardless of mileage. If the last time they were serviced is unknown, replace them right away.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Models with 4-cylinder engine:
BMW Z3 models with a 4-cylinder engine utilize one ignition coil (green arrow) with an individual ignition wire running to each spark plug (yellow arrows).
Figure 1

BMW Z3 models with a 4-cylinder engine utilize one ignition coil (green arrow) with an individual ignition wire running to each spark plug (yellow arrows). When servicing your spark plugs be sure the engine is cool and leave yourself about an hour to do the job. Be careful not to drop a spark plug, if you do, replace it. The spark plug insulator can crack and can lead to an engine misfire. Remove engine cover on cylinder head. See our tech article on engine cover removing.

Spark plugs - BMW supplied a small plastic tool (green arrow) used to remove the spark plug wires from the spark plugs.
Figure 2

Spark plugs - BMW supplied a small plastic tool (green arrow) used to remove the spark plug wires from the spark plugs. If it is missing, you can substitute a pair of soft-jawed spark plug wire pliers

Spark plugs - Using the supplied tool mounted under the engine cover (green arrow), pull up on ignition wire to remove from the spark plug.
Figure 3

Spark plugs - Using the supplied tool mounted under the engine cover (green arrow), pull up on ignition wire to remove from the spark plug. If the wire is stuck, try twisting it to remove. If you are having trouble gripping the tool, you can use a small screwdriver inserted into the tool to help. If you are only replacing the spark plugs, I suggest replacing one a time, this way you wonÂ't mix up the wires. You can also mark the cylinder location of the wires. If you find engine oil has contaminated the ignition wire boot you will have to repair the oil leak and replace the ignition wire. The source of the oil leak will likely be the cylinder head cover gasket.

Spark plugs - Using a 5/8 spark plug socket on a 12Â
Figure 4

Spark plugs - Using a 5/8 spark plug socket on a 12Â" extension, remove spark plug from cylinder head. Lightly lubricate new spark plugs with copper based anti-seize. Thread spark plugs into cylinder head by hand, this will prevent accidental cross-threading. Torque spark plugs to 25 Nm (18 ft-lb). Be sure to route ignition wire as it was before. Install engine covers and check your work.

Ignition Coil and Wires - When replacing your ignition coil or wires, be sure to note the location of each ignition wire before removing it.
Figure 5

Ignition Coil and Wires - When replacing your ignition coil or wires, be sure to note the location of each ignition wire before removing it. This way the order doesn'Â't get mixed up. BMW wires from the factory come with cylinder numbers on them. Do not depend on the numbering to be there when you purchase new wires.

Ignition Coil and Wires - If replacing the ignition coil, start by rotating the electrical connect counterclockwise to disconnect.
Figure 6

Ignition Coil and Wires - If replacing the ignition coil, start by rotating the electrical connect counterclockwise to disconnect. (green arrow).

Ignition Coil and Wires -Next you can remove the two 8mm nuts (green arrows) from the ignition coil mounting bracket studs.
Figure 7

Ignition Coil and Wires -Next you can remove the two 8mm nuts (green arrows) from the ignition coil mounting bracket studs.

Ignition Coil and Wires -Lift the ignition coil up and off the mounting bracket.
Figure 8

Ignition Coil and Wires -Lift the ignition coil up and off the mounting bracket.

Ignition Coil and Wires - Pull each wire off of the ignition coil towers.
Figure 9

Ignition Coil and Wires - Pull each wire off of the ignition coil towers. Usually the wires are stuck to the coil towers, you can gently release the wire using a flathead screwdriver by gently lifting the boot. Once free, pull off with a twisting motion.

Ignition Coil and Wires - Once the wires are detached from the coil, pull them out of the bracket (green arrow) that runs along the side of the cylinder head.
Figure 10

Ignition Coil and Wires - Once the wires are detached from the coil, pull them out of the bracket (green arrow) that runs along the side of the cylinder head. Note the position of the wires and the order they are installed. Cylinder #4 is on the top, #3 is next and so on.

Ignition Coil and Wires - Next remove each wire from the spark plugs.
Figure 11

Ignition Coil and Wires - Next remove each wire from the spark plugs. Then remove the wires from the bracket at the back of the cylinder head. Cylinder #4 (green arrow) is on the top, #3 (yellow arrow) is next and so on. The wires drop into this bracket and stack on top of each other. Be sure to take your time when routing the new wires. Get the fit and position right the first time. Once routed, install onto spark plugs. Install the new wires onto the ignition coil. Then reinstall the ignition coil. Start your engine once the coil is reinstalled and confirm your engine runs well. Then you can install the engine cover.

Models with 6-cylinder engine :
Models with 6-cylinder engine - BMW Z3 models equipped with a 6-cylinder engine utilize an individual ignition coil for each spark plug, referred to as coil over plug (green arrows).
Figure 12

Models with 6-cylinder engine - BMW Z3 models equipped with a 6-cylinder engine utilize an individual ignition coil for each spark plug, referred to as coil over plug (green arrows). When servicing your spark plugs be sure the engine is cool and leave yourself about an hour to do the job. Be careful not to drop a spark plug, if you do, replace it. The spark plug insulator can crack and can lead to an engine misfire. Remove engine cover on cylinder head. See our tech article on engine cover removing.

Models with 6-cylinder engine - Using a small flathead screwdriver; release ignition coil electrical connector retainer by prying up, then pull electrical connector out of ignition coil (green arrow).
Figure 13

Models with 6-cylinder engine - Using a small flathead screwdriver; release ignition coil electrical connector retainer by prying up, then pull electrical connector out of ignition coil (green arrow).

Models with 6-cylinder engine - Next remove two 10mm ignition coil fasteners (green arrows).
Figure 14

Models with 6-cylinder engine - Next remove two 10mm ignition coil fasteners (green arrows).

Models with 6-cylinder engine - Remove ignition coil from cylinder head by pulling straight up.
Figure 15

Models with 6-cylinder engine - Remove ignition coil from cylinder head by pulling straight up. If coil resists, twist when pulling up to break free from spark plug. The ignition coil rubber boot can become stuck to spark plug over time. If you find engine oil has contaminated the ignition coil boot you will have to repair the oil leak and replace ignition coil boot (or ignition coil). The source of the oil leak will likely be the cylinder head cover gasket.

Models with 6-cylinder engine - Using a 5/8 spark plug socket on a 12Â
Figure 16

Models with 6-cylinder engine - Using a 5/8 spark plug socket on a 12Â" extension, remove spark plug from cylinder head. Lightly lubricate new spark plugs with copper based anti-seize. Thread spark plugs into cylinder head by hand, this will prevent accidental cross-threading. Torque spark plugs to 25 Nm (18 ft-lb). Reinstall ignition coils and reconnect electrical connectors. Be sure to route wiring harness as it was before and connect ignition coil grounds. Install engine covers and check your work.

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Page last updated: Wed 12/7/2016 02:07:35 AM