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.
Computerized Engine Controls
The 900S, 9000S and all turbo models are equipped with a mass airflow meter to determine air density, altitude and air temperature. These measurements are then sent to the fuel injection system ECU.
The LH-Jetronic fuel injection system integrates the fuel injection and idle speed control functions into one system. Fuel injection system Electronic Control Unit (ECU) controls system functions.
The LH-Jetronic fuel injection system operates with moderate fuel pressure, held constant by a line pressure regulator. Fuel is metered into the cylinders by electrically controlled solenoid valves in the injectors. The injectors are installed just ahead of each cylinder intake valve.
Actual duration of injection (2-12 milliseconds) is determined by the ECU. The ECU receives several signals from various sensors and a mass airflow meter. Signals from mass airflow meter and exhaust gas oxygen sensor provide most of the information used by the ECU to maintain proper air/fuel ratios.
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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.