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.
Fuel Injection System - BOSCH LH: Description: Notes
The Bosch LH-Jetronic II fuel injection system has replaced the LH-Jetronic system that was formerly used. It has integrated the fuel injection and Constant Idle Speed (CI system) functions into one system. There is only one Electronic Control Unit (ECU) to control both functions.
The LH Jetronic II fuel injection system operates with a 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 aimed at the intake valve of each cylinder.
The duration of the injection, usually a few milliseconds, is determined by the ECU. The ECU receives several signals on various driving, engine and outside conditions from a set of sensors. The most important sensor in the system is the air mass meter.
The signals from the air mass meter and exhaust gas oxygen sensor provide most of the information used by the control unit to maintain proper air/fuel ratios. An idle speed adjustment screw has been provided in the throttle housing.
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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.