Idle Speed

Before attempting to set the idle speed:
a. Engine must be at full operating temp. (80°C/176°F)
b. All electrical consumers must be turned OFF (A/C and radiator fan should not operate while checking or adjusting).
c. A/C should be OFF
d. Fuel pressure gauge should not be connected.
e. If one or more fuel injectors were replaced, or fuel system was opened for any reason, rev engine up to 3000 rpm several times, then allow it to idle for two minutes before making any tests or adjustments.
f. Exhaust system must be in good condition, with no leaks.
g. Idle switch must be properly adjusted.
h. Remove cap from charcoal canister vent line tee fitting.
i. Remove PCV line and vent to atmosphere.

Fig. 13 Duty Cycle Test Connector (Located Between Near Right Strut Tower):

Adjusting Idle Speed By Duty Cycle

1. Connect a duty cycle meter (VW 1367 or equivalent) to the two terminal test connector (located near right strut tower) Fig. 13.
2. With the engine idling at 800 - 900 rpm, the duty cycle should be 28% - 30%, with oxygen sensor connected.
3. To adjust the duty cycle:
a. Turn air bypass screw, in throttle housing, in until it is firmly seated.
b. Slowly unscrew until duty cycle is within specification.







The idle speed on these cars is controlled by the ignition and injection control units with the idle control valve, timing and mixture adjustments. If the idle speed is not within specifications, check for air leaks, (between the throttle and the cylinder head, as well as between the throttle and the air flow meter), defective components, or faulty wiring. The idle speed is not adjustable.