When adjusting ignition timing, keep hands, equipment and wires well clear of the fan impeller.
This section describes the procedure for checking and adjusting the ignition timing on engines equipped with TCI. On engines with the Motronic control system, the ignition timing is determined in the electronic control unit and is not adjustable. The following procedure can be used to check the ignition timing, but no numerical values can be obtained, so if you have any concerns about incorrect ignition timing, please contact your BMW dealer.
This procedure requires some special tools. The engine must be at normal operating temperature and the air conditioner must be on (if installed) must be off. Make sure the idle speed is correct.
Tools for checking and adjusting ignition timing
1 - Vacuum Plugs - In most cases, the vacuum hoses will need to be disconnected and plugged. Plugs of various sizes and shapes can be used for this purpose if desired
2 - Strobe lamp with inductive sensor - Flashes a bright directional beam of light when spark plug #1 fires. Connect the wires in accordance with the instructions provided
3 — Distributor Wrench - On some models the mounting bolt is difficult to access with regular wrenches or socket heads. A wrench like this should be used
1. Set the parking brake and block the wheels to prevent the vehicle from moving. The transmission must be in neutral (manual) or Park (automatic).
2. The ignition timing marks are located on the engine flywheel (they can be seen through the ignition timing hole in the clutch housing) and/or on the torsional vibration damper on the front of the engine.
3. If a vacuum advance regulator is used, disconnect the vacuum hose from it.
4. Connect the tachometer and strobe lamp in accordance with the manufacturer's instructions (a lamp with an inductive sensor is preferable). Typically, the strobe light power wires are connected to the battery terminals, and the sensor wire is connected to the high-voltage wire of spark plug #1. Spark plug #1 is closest to the front of the engine.
If the strobe lamp with an induction sensor is not available, do not pierce the spark plug high-voltage wire to connect the strobe lamp control wire. If the high-voltage wire insulation is damaged, the secondary circuit voltage at the point of damage will short-circuit to the housing and the engine will malfunction.
Some models are equipped with a TDC transmitter to test the ignition system. However, to use it, a special BMW tester must be connected to the diagnostic connector, so if a special tester is not available, a standard strobe lamp should be used. The ignition timing marks may be located on the vibration damper, and if they are not there, there should be a TDC mark. If the strobe lamp has an adjustable delay, the ignition timing can be determined by first zeroing the measurement, and then rotating the adjusting device until the TDC marks are aligned, after which the ignition timing advance value is read from the strobe lamp. If a standard strobe lamp is used, then in accordance with the required ignition timing advance, apply a mark on the vibration damper and use the formula to calculate the distance from the TDC mark to the ignition timing mark:
Distance =
where p = 3.142
r = radius of the damper
advance = required TDC advance in degrees
5. With the ignition off, loosen the distributor bracket nut until the distributor can turn without slipping.
6. Make sure the strobe light wires are clear of the drive belts and fan, then start the engine.
7. Increase engine speed to the required value and then aim the flashing strobe light at the spark marks - be very careful with moving engine parts.
8. The mark on the flywheel or vibration damper should appear to be stationary. If it is aligned with the required mark on the clutch housing or front engine cover, the ignition timing is correct.
Ignition mark "OT" on the flywheel.
Ignition mark "OZ" on the flywheel.
9. If the marks are not aligned, adjustment is required. Very slowly rotate the distributor until the marks are aligned, taking care not to touch the high-voltage wires.
10. Tighten the distributor bracket nut and check the ignition timing again.
11. Stop the engine and disconnect the strobe light and tachometer. Connect the vacuum hose, if equipped.