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, please refer to chapter 4A).
The vehicles described are equipped with a distributorless ignition system, which uses two twin ignition coils. The duality is that each coil has two high voltage terminals. On early models, the ignition coils were housed in a single housing mounted on the left end of the cylinder head. Four high voltage wires connect the coil terminals 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 #1 and #4, and the other serves cylinders #2 and #3).
Being under the control of the BEU, the ignition coil operates on the principle of "idle spark". Spark plugs are activated in pairs, twice for each complete engine cycle. In this case, one of the two "activated" cylinders will be on the compression stroke (and the air-fuel mixture in it will ignite), and the other one at this time will be in the process of release. Since the ignition spark during the exhaust phase has no effect, it is "wasted", hence the term "wasted spark." The ECU uses input signals from various sensors to calculate the required ignition advance angle and the duration of the coil's power supply.
Some models have a knock sensor built into the ignition system. The sensor is located on the cylinder block and prevents engine detonation under load. The sensor is sensitive to vibration and detects detonation, which occurs when pre-ignition occurs in the engine. The knock sensor sends an electrical signal to the ECU, which in turn reduces the ignition timing until the detonation stops.