Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Ignition, basic function
- Idling speed ignition timingÂ
When idle speed control is active, the ignition timing is adjusted to stabilize idling speed. The value is sent to box 3.
- Normal ignition timingÂ
When the idle speed control is not active, the ignition timing is obtained from a load and speed-dependent matrix. The matrix value is optimized for the lowest fuel consumption (best torque). The value is sent to box 3.
- Selection of ignition timingÂ
One of the ignition timing calculations is selected, depending on which function is active. The value is sent to box 6.
- Catalytic converter heating ignitionÂ
In order to heat the catalytic converter as fast as possible after starting, the ignition will be retarded. The value is load and engine speed dependent.
- Engagement of catalytic converter heating ignitionÂ
The function is active when the coolant temperature is above -8°C and below +35°C.
- TotalÂ
The value from box 5 is added to the value from box 3.
- CompensationÂ
The ignition timing is corrected depending on the engine coolant temperature and intake air temperature. The value is sent to box 6.
- Knock controlÂ
If knocking occurs, the amount by which the ignition should be retarded is calculated. The value is sent to box 6.
- TotalÂ
The compensation angle and knock retardation are added to the current ignition timing. The value is sent to box 7.
- Selection of ignition timingÂ
Starting ignition timing is selected when the engine has not yet started. The value is sent to box 9.
- Starting ignition timingÂ
Starting ignition timing is calculated depending on intake air temperature and engine coolant temperature. The value is sent to box 9 via box 7.
- Activate relevant triggerÂ
At the calculated crankshaft angle, the microprocessor controls the transistor for the trigger which is next in the firing order.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.