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 Cis (Lambda) System: Description
The Bosch Continuous Injection System is a hydraulic-type fuel injection system which uses an air flow sensor (mechanically connected to a hydraulic valve) to control injection quantity.
The Lambda system is a feedback control capable of measuring air/fuel ratios and correcting them constantly. The combination of the two systems makes it possible to obtain economy and performance, while minimizing exhaust emissions. See Fig 1.
The system consists of the mixture control unit (air-flow sensor and fuel distributor), control pressure regulator, auxiliary air valve, cold start valve, thermo-time switch, injector nozzles, fuel pump, filter, oxygen sensor, electronic control unit, frequency valve, and catalytic converter. Some models use additional components, such as a thermo-vacuum valve, hot start pulse relay, or a constant idle speed control system.
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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.