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.
BOSCH LH-JETRONIC - Engine Control System: Description
The Volvo Computerized Engine Control System is used on all Volvo 4-cylinder engines except GLT Turbo. It consists of a computer controlled electronic ignition system and Bosch LH-Jetronic II fuel system with integrated Constant Idle Speed system.
The computer controlled ignition system consists of Volvo breakerless distributor, an electronic control unit, ignition coil, ignition switch, throttle switch and knock sensor. The distributor contains no vacuum or centrifugal advance mechanisms. The rotor and armature are a single unit. See Fig 1 .
A Hall Effect sending unit in the distributor provides engine speed signals to the electronic control unit. The distributor also consists of necessary connecting wiring and a distributor cap.
The fuel system includes an electronic control unit, ignition coil, ignition switch, system relay, fuel system components, A/C switch, airflow meter, air control valve, starter motor, throttle switch, coolant temperature sensor, oxygen sensor and connecting wiring and hoses.
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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.