bmwrepairs: How to test and replace Spark Plug wires on 2005 BMW 325?

Spark Plug

This is complete detail,for testing and replacing spark plugs and its wires:---

Removal & Installation

Fig. Label each spark plug wire before disengaging and/or disconnecting them one at a time

Fig. Remove the spark plug cover fasteners-M42 and M44 engines

Fig. Removing the spark plug wires with the supplied tool-M42 and M44 engines

Fig. Removing the valve cover trim plugs-M50, S50, M52 and S52 engines

Fig. Remove the trim cover fastener plugs-M50, S50, M52 and S52 engines

Fig. Removing the valve cover trim mounting nuts-M50, S50, M52 and S52 engines

Fig. Remove the oil filler cap, and immediately cover the opening, then remove the valve cover trim cover-M50, S50, M52 and S52 engines

Fig. Once the trim cover is removed, the coil packs are clearly visible-M50, S50, M52 and S52 engines

Fig. Release the electrical connector by moving locking bar-M50, S50, M52 and S52 engines

Fig. Detach the electrical connector from the coil pack-M50, S50, M52 and S52 engines

Fig. Remove the coil pack fasteners-M50, S50, M52 and S52 engines

Fig. Remove the coil pack by carefully lifting upward-M50, S50, M52 and S52 engines

Fig. This spark plug cavity was cleaned with compressed air before the spark plug was removed. Note the absence of any debris-M44 engine shown

Fig. After the spark plug cavity is cleaned, you can remove the spark plug-M50 engine shown

Fig. Inspect the condition of the spark plug once it is removed

The spark plug replacement intervals for BMW models vary depending on model, the type of driving and mileage. The Service Indicator located in the instrument determines the maintenance intervals based on information collected by the Engine Control Module (ECM). Vehicles driven in severe conditions such as stop and go driving require more frequent maintenance than those driven primarily on highways, therefore because the maintenance interval is determined by the Service Indicator, the service intervals will vary.

The spark plugs are replaced during the BMW Inspection II maintenance procedures, which by mileage averages between 30,000-40,000 miles. If the vehicle is not driven frequently enough to attain the mileage recommended for the Inspection II maintenance procedures, it's a good idea to have maintenance performed based on time. Although a time interval is not directly stated, due to the fact that the 3 Series and Z3 BMWs use aluminum cylinder heads, it's a good idea to replace the spark plugs every 2-4 years to avoid the chance that the protective coating on the spark plug may react with elements such as condensation and corrode in place.

BMW recently approved the use of high performance platinum spark plugs in some models. These plugs can be identified by a platinum plated center electrode surrounded by four ground electrodes and features a maximum service life under normal operating conditions of 100,000 miles (160,000 km). Other claimed benefits of these spark plugs include:

Improved cold starting performance

Less susceptible to misfire during all operating conditions

Improved operation in stop and go traffic and short distance driving

More consistent operation throughout the service life of the spark plug

Improved fuel combustion qualities, including improved idle quality and acceleration

For specific details and availability of these spark plugs consult your local BMW dealer and refer to the service information bulletin in Group 12 numbered 12 01 99.

Refer to the maintenance interval chart located in the vehicle owner's manual or at the end of this section for additional items to be checked during the recommended maintenance services. During normal operation, The spark plug's gap increases as it wears. As the gap increases, the plug's ability to conduct a spark decreases, therefore the necessary voltage required to conduct a spark increases. The voltage required to jump the spark plug's gap at high engine speeds is about two to three times as much than at idle. The improved air/fuel ratio control of modern fuel injected engines combined with the higher voltage output of their ignition systems, will often allow an engine to run significantly longer on a set of spark plugs. However, the engine's efficiency most likely will drop as the spark plug gap widens and may decrease both fuel economy and power).

Before removing the spark plugs, label, or arrange the ignition coil leads or spark plug wires to ensure reinstalling them in the correct positions. On vehicles equipped with a distributor cap, mark the position of the spark plug wire for the number 1 cylinder. If for some reason the wires do become mismatched, the correct sequence can be easily determined by using the engine's firing order. The original equipment spark plug wires are very high quality, however because the spark plug wires conduct a high energy electrical current, the insulation of the wires must be kept clean and not allowed to rub against any object that may damage the insulation.

When removing the spark plugs, remove them one at a time in a logical order, noting which cylinder from which they were removed. A careful inspection of the spark plugs is one method of evaluating the engine's operating conditions. Spark plugs showing signs of a carbon build up or deposits around the center electrode, may be indications of an impending electrical or mechanical failure.

NOTE

Remove the spark plugs when the engine is cold, if possible, to prevent damage to the threads. If removal of the plugs is difficult, apply a few drops of penetrating oil or silicone spray to the area around the base of the plug, and allow it a few minutes to work.

To replace the spark plugs, proceed as follows:

Make sure the ignition is OFF .

On S14 and B20 engines:
1. Label the spark plug wires and note their location or replace one spark plug at a time, to ensure proper reassembly for each spark plug wire and spark plug.
2. Carefully remove the spark plug wire(s) from the spark plug(s). Pull only on the boot; do not pull on the wire itself otherwise the wire and connector will be damaged.

On M42 and M44 engines:
1. Turn the spark plug cover slotted fasteners ¹ / ₄ (90°) turn clockwise and remove, then remove the cover by carefully lifting it upward.
2. Label the spark plug wires and note their location or replace one spark plug at a time, to ensure proper reassembly for each spark plug wire and spark plug.
3. Use the spark plug wire pulling tool located under the cover to remove the spark plug leads.

On M50, S50, M52 and S52 engines:
1. Remove the valve cover trim fastener caps, the remove the fasteners securing the trim to the valve cover.
2. Remove the oil fill cap and place a clean rag in the oil filler cavity to prevent debris from falling into the engine. On M50 engines it may be necessary to remove the fuel injector rail trim cover before removing the valve trim cover. The fuel injector rail cover is removed in the same method as the valve cover trim.
3. Release the clips for the coil pack electrical connectors, disconnect and place the coil wiring harness aside. Make sure not to note the correct location for each coil's electrical connection.
4. Remove the fasteners securing the coil packs.
5. Note the coil pack location for correct reinstallation, then carefully lift the coil packs upward and set aside to expose the spark plug hole cavities.

If compressed air is available, blow out the recessed cavities in which the spark plugs are located.

Use a spark plug socket and extension, and place over the spark plug. Loosen the spark plug ¹ / ₈ a turn (45°) counterclockwise and if compressed air is available, blow out the recessed cavity in which the spark plug is located a second time.

Remove the spark plug. Inspect the plug and plug gap as outlined in this section, and replace as necessary.

To install:

Check and adjust the spark plug gap as necessary. If the plug has dual electrodes, the gap should not be adjusted, and if out of specification the plug should be replaced. Always check the gap of a new plug to make sure it hasn't been damaged during packaging or shipping. Some spark plugs come pre-gapped and should not be gapped. Consult the spark plug's manufacturer for plug gapping information.

Apply a light coat of an anti-seize compound the threads of the spark plug, unless directed otherwise by the spark plug manufacturer.

Place the spark plug in the socket or use a piece of rubber hose placed over the spark plug porcelain to place the plug in the spark plug hole.

WARNING

Always carefully thread the plug by hand to prevent the possibility of crossthreading and damaging the cylinder head's threaded spark plug hole.

Thread the plug into the cylinder by hand until the spark plug seats. Do force the spark plug or use a wrench to get it started, to prevent crossthreading. The spark plug should thread in easily by hand. If it doesn't, check the threads for damage or debris.

Using a torque wrench, tighten as follows:

Spark plugs with M12 x 1.25 threads: 15-19 ft. lbs. (20-23 Nm)

Spark plugs with M14 x 1.25 threads: 22-24 ft. lbs. (29-33 Nm)

On S14 and B20 engines:
1. Replace the spark plug wire(s) to the correct location onto the spark plugs.

On M42 and M44 engines:
1. Reinstall the spark plug wire and press downward carefully but firmly to seat it. Install the spark plug cap removal tool into its holder then snap the cover into place
2. Reinstall the slotted cover fasteners and secure them by turning it ¹ /₄ (90°) of a turn counterclockwise.

On M50, S50, M52 and S52 engines:
1. Replace the coil packs on the spark plugs and tighten the nuts. If equipped, make sure to reinstall all ground straps for Nos. 1 and 6 coil packs.
2. Attach the wiring harness connector and lock down the connector bar.
3. Replace the valve cover trim and if removed, the fuel injector rail cover and reinstall their fasteners and fastener trim covers.
4. Install the oil filler cap.

M42 Engines

Turn the ignition switch to the OFF position.

Remove the fasteners holding the two halves of the guide channel together and separate the housing from the valve cover.

Turn the slotted fasteners on the valve cover trim ¹ / ₄ turn (90°) clockwise and remove the trim cover.

Note and label the wires and their original location.

Use the supplied tool located under the cover to release the plug wire(s) from the spark plug(s) and disconnect the ignition lead(s) from the ignition coil.

Installation is the reverse of the removal procedure, making sure to correctly route the plug wire and make sure it snaps into place when installed onto the coil and spark plug.

Fig. Spark plug wire routing-M42 engine shown

M44 Engines

Turn the ignition switch to the OFF position.

Remove the electrical harness from the ignition coil pack by rotating the locking collar counterclockwise.

Remove the ignition coil mounting nuts and place the coil pack aside near the valve cover.

Turn the slotted fasteners on the valve cover trim ¹ / ₄ turn (90°) clockwise and remove the trim cover.

Note and label the wires and their original location.

Use the supplied tool located under the cover to release the plug wire(s) from the spark plug(s) and disconnect the ignition lead(s) from the ignition coil.

Fig. The trim cover on the 4-cylinder engine is removed by turning the mounting fasteners clockwise 90°

Fig. With the fasteners released, simply lift the trim cover off

Fig. The spark plug removal tool is located under the trim cover

Fig. Slide the removal tool onto the plug wire cap. On stubborn connectors, rotate the cap side-to-side while pulling upward

Fig. Remove the ignition coil harness connector by rotating it counterclockwise-M44 engines

Fig. The plug wire bracket is attached to the valve cover with two captured bolts

Fig. The plug wire bracket, connectors and insulating tray are lifted off and placed aside

Fig. Always label the plug wires to ensure correct installation

Fig. When detaching the plug wire, pull on the boot only, not on the wire itself

To install:

Installation is the reverse of the removal procedure, making sure to correctly route the plug wire and make sure it snaps into place when installed onto the coil and spark plug.

S14/M20 Engines

Turn the ignition switch to the OFF position.

Note and label the installed location of the wires.

Unplug the spark plug wire(s) from the distributor cap.

Release the plug wire(s) from the spark plug(s) and disconnect the ignition lead(s) from the ignition coil.

Installation is the reverse of the removal procedure, making sure to correctly route the plug wire and make sure it snaps into place when installed onto the coil and spark plug.

Testing

Fig. Checking plug wire resistance through the distributor cap with an ohmmeter

Fig. Checking individual plug wire resistance with a digital ohmmeter

At every tune-up/inspection, visually check the spark plug cables for burns cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil. Replace any damaged wiring.

Every 50,000 miles (80,000 km) or 60 months, the resistance of the wires should be checked with an ohmmeter. Wires with excessive resistance will cause misfiring, and may make the engine difficult to start in damp weather. The spark plug wire resistance should be 4500-5500 ohms.

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This will help.

Thanks.

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