1983 AU Car Idle speed

Hello Foxint,

Your 1982 Porsche 928 Euro/ROW uses Bosch CIS fuel injection, whereas the US/Japan models used Bosch L-Jetronic fuel injection. Your engine should idle at 650 - 750 RPM (US/Japan are speced at 725 - 800).

The CIS injection CO % (air/fuel ratio) should be 1.0 to 2.0% measured at the tail pipe. The adjustment is at the fuel distributor. It is a VERY sensitive adjustment. The screw only needs to be turned a small amount for a change. It is getting difficult to find a garage that has a CO% meter since most modern cars no longer have air/fuel adjustment. The 1987 and newer 928s have no adjustment. A shop that services old cars with carburetors may have such equipment.

[US/Japan cars use a catalytic converter, CO% cannot be measured at the tail pipe which is after the catalytic converter, the spec is 0.4 to 0.8% CO before the catalytic converter].

If the idle speed doesn't change at the screw, the port may be plugged. Idle speed is increased by allowing more bleed air into the air intake system.

The 928 tachometer may not be very accurate at low speeds. An external tach may provide a more accurate reading.