Every time you tune-up or at the time of inspection, make sure that you carry out a visual check for burns, cuts or cracks in the wires' insulation. Also, inspect boots and nipples on distributor cap or coil then replace any damaged wiring. In order to ascertain their resistance levels, an ohmmeter should be used to measure the spark plug wire every 50,000 miles or 60 months. This is because wires having increased resistance will result in misfiring thereby making it hard for an engine to start during damp weather. Spark plug wire resistance should fall within a range of 4500-5500 ohms. While removing and installing spark plug wires, switch off ignition then take off the wires from the distributor cap. Remove the wires from plugs and disconnect ignition leads from ignition coil. Reverse installation procedure ensuring that wires are routed properly and snap into place on the coil as well as on spark plugs. When removing or replacing a distributor cap and rotor ensure that no damage occurs by positioning thin cardboard between radiator and fan with ignitions off.Locate all wires just as they were originally before labeling them so that after finally removing distributor caps these can be removed easily from there.Remove screws while checking if seal is still okay otherwise change it.Screw out hex head bolts to take out rotor.Put rotor onto its shaft again tightening hex head bolts.Reinstall distributor cap together with seal fastening mounting screws.Replace ignition leadings at the right terminals also put cover under clip.Check both cap as well as rotor for any indication of burning, excessive corrosion on contacts or carbon tracks which needs replacement.The timing of ignition in some models of BMW cannot be adjusted manually since it is automatically controlled by DME control unit according to engine conditions.
