General information
The ignition system is integrated with the fuel injection system. Together they form an integrated engine management system controlled by a single electronic control unit (for more information refer to chapter 4A).
The described vehicles are equipped with a distributorless ignition system, which uses two dual ignition coils. Duality lies in the fact that each coil has two high voltage outputs. On early models, the ignition coils are housed in a single housing mounted on the left end of the cylinder head. Four high voltage wires connect the coil leads to the spark plugs. On later models, the ignition coils are housed in a single housing mounted directly above the spark plugs. There are no high voltage wires.
Each of these two coils serves two cylinders (one serves cylinders No. 1 and 4, and the other serves cylinders No. 2 and 3).
Under the control of the BEU, the ignition coil works on the principle «idle spark». The spark plugs are fired in pairs, twice for each complete engine cycle. However, one of the two «activated» cylinders will be on the compression stroke (and the air-fuel mixture in it will ignite), and the other at this time will be in the process of release. Since the ignition spark does not affect anything during the exhaust stroke, it «wasted». Hence the term «idle spark». The ECU uses input from various sensors to calculate the required ignition timing and duration of the coil.
Some models have a knock sensor built into the ignition system. The sensor is located on the cylinder block and prevents «detonation» engine under load. The sensor is sensitive to vibration and detects knocking that occurs when the engine pre-ignites. The knock sensor sends an electrical signal to the ECU, which in turn advances the ignition until the knock stops.