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 Cis: Description
The Bosch Continuous Injection System (CIS) is a hydraulic-type fuel injection system which uses an air flow sensor, that is mechanically connected to a hydraulic valve, to control injection quantity.
The Lambda system is a feedback control capable of measuring air/fuel ratios and constantly correcting them. The combination of the two systems makes it possible to obtain both 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.