Idle Speed/Throttle Actuator - Electronic: Testing and Inspection
Checking The Idle Air Control ValveIdling speed drops appreciably when the engine load is increased suddenly in connection with the engagement of a high current-consuming item of equipment, such as the A/C, ACC, power steering, electrically heated rear window or the automatic transmission when a gear is selected.
Tools:
- Pliers
- ISAT scan tool
1 Checking for air leakage.
Start the engine and warm it up. Then run it at idling speed.
2 Restrict the flow of air through the idle air control valve by pinching the air hose with a pair of ph- ers. Idling speed should drop substantially. Do not pinch the hose so hard that the engine stalls.
3 If engine speed drops, continue with point 5.
4 If engine speed does not drop, continue fault diagnosis by checking:
- Incorrectly adjusted throttle
- Air leakage (after the throttle), e.g. leaky purge valve on the emission canister.
5 Check the idle speed control function. Remove the air flow restriction. Idling speed should increase appreciably and then stabilize after 10 - 20 seconds at the normal idling speed of 850 rpm (engine warmed up).
6 If operation of idling speed control is OK, continue with point 18.
7 If it is not OK, continue with point 8 or 11, depending on which LH system the car has.
8 LH 2.4, 2.4.1 and 2.4.2. Checking the operation of the control valve.
Disconnect the valve's hoses.
Remove the idle air control valve.
Plug in the idle air control valve connector.
Connect the ISAT scan tool (LH 2.4, 2.4.1 and 2.4.2. M1990-).
Turn the ignition switch to the ON position.
Select command code 553 or self diagnostics 2.4, 2.4.1 or 2.4.2 M1988-.
Check visually that the valve rotates without displaying any tendency to bind.
9 If the control valve is OK, continue with point 14.
10 If the control valve binds or jams, change the idle air control valve.
11 LH 2.2 Check that battery voltage is present on pin 2 and that the voltage varies on pins 1 and 3.
12 If the voltage is Ok, change the idle air control valve.
13 If the voltage is not OK, check the wiring connected to the LH control module.
14 Check the idle air control valve contacts and connector.
Inspect the valve's contacts and connector visually. If necessary, clean and lubricate the contacts/connector with KONTAKT 61, part No. 30 04 520.
15 Check whether engine speed still drops.
16 If it does, continue with point 18.
17 If it does not, continue with point 22.
18 Checking engine load.
Check that the LH control module input is of the correct level to compensate for possible load changes.
Depending on the type of problem, continue fault diagnosis with:
- Fault diagnosis, DRIVE. ISAT scan tool code 45723/25723
- Fault diagnosis as in "Checking change in idling speed on engagement of A/C compressor (cars with idle air control valve), not ETS".
- Fault diagnosis, other problems. Continue with the following points:
19 Try fitting a replacement idle air control valve. Check whether the engine works.
20 If engine speed still drops, continue with point 22.
21 If it does not, change the idle air control valve.
22 Final check.
Test drive the car and check whether the fault symptoms persist.
23 If the fault symptoms persist, change the LH control module.
24 If the fault symptoms are no longer present, it indicates that the remedial measure taken was correct or that the fault is of intermittent type.