Genuine Audi Idle Control Valve

Audi Idle Control Valve Parts and Q&A

• Idle Speed Control
  078-133-455-A
  Q: How do the Idle Control Valve and Throttle Position Sensor function in relation to engine speed and air conditioning on Audi 90?

  A:

  The two-way valve I increases engine speed when it drops below 700 rpm, with the control unit located beneath the facia, while the two-way valve II activates when the air conditioner is switched on. To check valve I, lower the engine speed using the adjustment screw and ensure it increases at 700 rpm; squeezing hose 1 should cause the speed to drop. With the hose clamped, adjust the idling speed to the specified value, then unclamp the hose to verify the engine speed rises to 1050 rpm before dropping back to normal. For valve II, allow the engine to idle, squeeze the hose, and confirm no change in speed; after switching on the air conditioning, the speed should drop. To inspect the airflow meter plate, remove the air duct, disconnect the coil HT lead, and operate the starter for ten seconds, then lift the plate to check resistance across its movement range. The free travel of the plate should be 0.5 to 3.0 mm for the DZ engine and up to 2.1 mm for KV and PS engines, adjustable at the control plunger stop. For the cold start valve and thermotime switch, disconnect the HT cable from the ignition coil, then the wiring plug from the cold start valve, connecting a diode test lamp to the terminals. Disconnect the thermotime switch plug, earth the green/white wire, and operate the starter to check the test lamp lights. Refit the plug to the switch while keeping the green/white wire earthed, then remove the cold start valve to check the spray pattern, ensuring it remains dry for at least a minute. With the valve refitted and the plug disconnected, connect a diode test lamp across the terminals, operate the starter, and confirm the lamp lights for one to eight seconds based on coolant temperature. The cold acceleration enrichment activates when the thermotime switch, diaphragm pressure switch, and throttle valve switch are closed; after starting the engine and letting it idle, the test lamp should not light, but it should briefly light when the throttle is quickly opened. For the diaphragm pressure switch, disconnect the wiring, run the engine at idle, and check resistance with an ohmmeter, ensuring it reads infinity. Opening the throttle should cause a brief drop in resistance. For the throttle valve switch, disconnect the wiring plug, connect an ohmmeter, and confirm infinity resistance with the throttle closed; slowly opening the throttle should register infinity resistance until the switch contacts close, with the gap between the idling stop and throttle lever set between 0.2 and 0.6 mm. For the auxiliary air valve, disconnect the HT lead, connect a diode test lamp across the plug terminals, and operate the starter to check the lamp lights. After reconnecting the HT lead, start the engine, squeeze the hose between the auxiliary air valve and inlet manifold, and ensure the engine speed drops. Reconnect the wiring plug and repeat the test with the engine warm, confirming no change in speed. For the warm-up valve, disconnect the HT lead, connect a diode test lamp across the plug terminals, and operate the starter to check the lamp lights. The basic throttle valve setting is typically factory-set and should not require adjustment; if disturbed, loosen the nut, unscrew the adjusting screw to create a gap, turn it clockwise until it just touches the stop, then turn it an additional half-turn, applying locking fluid to the nut threads before tightening while holding the screw stationary, and check the idling settings after adjustment.
• Idle Speed Control
  034-133-455-B
  Q: What precautions should be observed before working on the Idle Control Valve in the fuel system on Audi 100?

  A:

  Observe the precautions before working on any component in the fuel system. A cold spray will be required to cool the expansion element in the following procedure. The fast idle speed is controlled by an electrically heated expansion element located on the top of the injection pump. With the engine cold, the idle speed is increased to 900 ± 50 rpm, and after a maximum period of two minutes, the engine speed returns to normal. The engine must be at normal operating temperature before carrying out this procedure, and all electrical accessories must be switched off. Apply the handbrake and select neutral, ensuring the cold start knob is pushed in to the fully off position. Start the engine and allow it to idle. Disconnect the wiring from the expansion element, then use the cold spray to cool the element to a temperature below 30° C, causing the engine idle speed to increase to 900 ± 50 rpm. If the fast idle speed is incorrect, loosen the locknut on the expansion element and turn the element until the correct idle speed is obtained, then tighten the locknut. Connect the wiring to the element and check that the engine speed returns to normal within two minutes. If the expansion element does not function correctly, it must be renewed.