Tools needed when changing spark plugs
1 - Candle head - Equipped with a special elastic insert, which excludes the possibility of accidental damage to the porcelain insulator when the candle is turned out.
2 - Torque wrench - Not a mandatory tool, provides a reliable guarantee of the correct tightening torque of the spark plugs.
3 - Ratchet drive - Used in conjunction with a candle head and a torque wrench.
4 - Extension - Depending on the model and its accessories, access to spark plugs can be limited to varying degrees, so the use of extensions of the appropriate shape and design will greatly facilitate the procedure.
5 - A device for measuring and correcting spark plug gaps - Several types of this kind of tools are available - make sure that the tool is equipped with a feeler gauge that matches the size of the spark plug gaps in your car.
1. Before starting work, prepare all the necessary tools, which include a replaceable spark plug head and a set of feeler blades. Some spark plug manufacturers supply special tools to measure the spark plug gap.
2. The best way to replace spark plugs is to buy new spark plugs in advance, adjust their gap, and replace each spark plug in turn. When buying candles, it is very important to choose exactly those candles that are designed for the engine of your car. Information about them can be found in the Specifications.
3. With new spark plugs on hand, let the engine cool completely before removing the old ones. During this time, you can inspect new spark plugs for defects and check spark plug gaps.
4. The spark plug gap is checked by inserting a gauge of the desired thickness between the electrodes at the end of the spark plug. The gap must correspond to that specified in the Specifications. The wire should only touch each of the electrodes. If the gap is not correct, slightly bend the bent part of the electrode using a knurled adjuster until the desired gap is reached.
When adjusting the gap of a new spark plug, bend only the ground electrode base without touching its end. If the ground electrode is offset from the center electrode, use the knurled adjuster to align them. Check the porcelain insulator for cracks, indicating that the spark plug needs to be replaced.
Spark plugs should only be replaced when the engine is cold or slightly warm. If the spark plugs are turned out on a hot engine, the threads in the holes in the light metal cylinder head may be damaged.
5. Turn off the ignition.
6. Engines 316i, 318i: Disconnect the spark plug connector in a vertical direction. When doing this, pull up on the cable, not on the plug.
Engines 320i, 323i, 328i
7. Remove an element of the air filter of ventilation of salon of system of heating and the conditioner, address to the Section Replacing the Cabin Air Filter Element.
8. Disconnect the cable channel at the bottom of the filter housing -2- by opening the clips and remove the cable.
9. Remove the screws -1- with a Torx T30 screwdriver and remove the lower part of the air collection box -2-.
10. Remove the oil fill plug.
11. Pry with a screwdriver and remove the covers of the mounting bolts (arrows on the accompanying illustration), remove the two screws underneath.
12. Disconnect the connector of each ignition coil by pulling up on the plugs.
13. Turn away bolts of fastening at each coil of ignition, carefully take out coils.
Pay attention to the cylinder head cover grounding straps on cylinder coils 1 and 6. When installing, they must be re-attached to their original places.
14. If possible, blow out the spark plug recesses with compressed air to keep dirt out of the cylinder bores.
15. Remove the spark plugs with the appropriate spark plug wrench. When doing this, make sure that the key does not warp, as this can damage the ceramic insulator.
Examination
16. Check the condition of the spark plugs. Compare the removed candle with those shown in the pictures in Section Charge and launch systems, this will give you useful information about the general condition of the engine. An oily spark plug indicates a malfunction or a bad piston ring seal. You can check the presence of a mechanical defect in the spark plug using a compression gauge, refer to the appropriate section.
Installation
17. Screw in the spark plugs by hand with a spark plug wrench until they touch the cylinder head. Caution: Be careful not to distort the spark plugs.
18. Tighten the spark plugs to 25 Nm.
If a torque wrench is not available, tighten the new spark plugs 90° (1/4 turn). Used spark plugs should only be tightened by 15°.
19. Engines 316i, 318i: Put a plug on each candle. The plug must be clearly engaged. Do not confuse the plugs, they are numbered, with the first cylinder at the front in the direction of travel.
Engines 320i, 323i, 328i
20. Put the ignition coils on the candles and secure them. Fix the plugs on the coils with brackets. Attach ground straps to ignition coils for cylinders 1 and 6.
21. Fix the mass tire -3 - of the connecting plate of the coils to the front bolt of the ignition coil. The earth bar -1- of the cable duct must be bolted to the connecting plate -2- of the spark plugs.
22. Bolt the engine cover.
23. Screw on the oil filler cap.
24. Attach the bottom of the air box.
25. Route the cable into the conduit at the bottom of the air box. Close the cable channel.
26. Reinstall the air filter element of the heating and air conditioning system, refer to Section Replacing the Cabin Air Filter Element.
Restoring spark plug threads
If there is damage to the thread for the spark plugs, it must be repaired. Suitable tools and repair kits are available for this, for example from BERU. The old thread is drilled with a special drill, for which it is not necessary to remove the cylinder head. Then a new thread is cut in the head and a candle with a special threaded insert is screwed in. The insert sits securely and tightly.