Top Tip : Idle Air Value, Activated by the ECU to either mechanically or pneumatically control the idle speed of the engine. A secondary use of the valve is to reduce emission by allowing air to enter the engine on overrun conditions. failure symptoms are stalling and or sticking idle. pneumatic valve can often be cleaned as a temporary test, with mechanical stepper motor type’s failure is irreparable

Heater Control Valve, This Controls the flow of The engines Coolant through The Heater Matrix. Failure symptoms of the Heater Control Valve are that it lack of control of the heater, ie too hot or too cold in the passenger compartment and the other is that the unit is leaking coolant. Failure is often caused by lack of use. Check its operating during service and inspect for leaks.

Knock Sensor, This sensor is a piezo based sensor that attaches directly to the engine and electronically listens to the engine. The ECU responds to any signal of pinking or detonation by retarding the ignition timing. failure symptoms are lack of performance or increased fuel consumption. Check for corrosion or make sure that it is correctly fastened to the engine.

Coolant Temperature Sensor, this sensor measures the temperature of the engines coolant and signals the ECU to adjust the fuel mixture. Failure symptoms are poor performance, Hard to start or misfire. Inspect Every 12,000 – 15,000 miles. Replace coolant if failure occurs if problem still remains replace sensor.

The Air Temperature, this sensor is in the intake manifold. The sensor’s resistance changes as the temperature increases or decreases. The ECU receives this change in signal and adjusts the injector pulse width and fuel mixture accordingly. failure symptoms are hat the Engine Check light is on continuously, hesitation or strong exhaust odour. poor performance or economy. Inspect for damage or corrosion on terminals when error code’s indicate a problem in the system.

Cam / Crank Sensors these sensors determine camshaft and crank shaft position and sends this information to the ECU. The computer uses this to calculate injector on time and ignition system timing. Failure symptoms are engine warning light on dash, hard starting and poor drivability. there is no scheduled service, the part must be replaced when failure occurs.

Evaporation Control Valve controls the emissions of fuel vapour from the fuel tank. Direct the sole fuel tank ventilator to either the carbon trap or the inlet manifold. Can be electronically or pneumatically controlled. failure symptoms are that the car may have poor drivability at low RPM or the complain of fuel smell in the car. To fix simply replace and check connecting pipes for splits / damage

EGR Valve also known as the Exhaust Gas Recirculation Valve or the EGR solenoid, This valve reduces the HC emissions of an engine by reducing the combustion chamber temperature. This is achieved by routing a a portion of dirty exhaust gasses into the inlet system. Later types are electronically operated whereas early systems are purely pneumatic. Failure symptoms are increased (CO), Poor low-speed drivability, and difficult hot starting. Failure is as a result of carbon from the engine, thus a worn engine will cause premature failure of the valve.

This part Monitors the throttle opening and closing for the ECU to adjust the fuel flow. Failure symptoms Hesitation, emissions failure flat spot or stalling when at a stand still.

Weekly Tip: Oxygen Sensor also known as a Lambda sensor, This unit monitors the oxygen content of exhaust gas to help maintain the correct Air/Fuel ratio in petrol cars.this ensures the catalytic converter is working at maximum efficiency.