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TOPIC: 1983 AU Car Idle speed

1983 AU Car Idle speed 13 Sep 2019 21:17 #20954


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Hi Guys.

Been without my 1983 928 for almost 2 years. Now doing some shake-down driving. Drove it to Sydney (about 400km) 2 years ago and drove it back on Sunday (2019-09-08).

Lots of things not working at the beginning of the trip and some now working…ha-ha….

My stupid question as google was unable to tell me:

What is the recommended idle speed for the 1983 AU (World model) mine seems not to want to go above 400rpm. The idle adjustment screw seems to do nothing???

D
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1983 AU Car Idle speed 14 Sep 2019 19:32 #20963


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what happens when you switch on the air AC, does the idle speed go up or down.
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1983 AU Car Idle speed 14 Sep 2019 19:59 #20964


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Hi Karma
Thank you for the reply.
I made a mistake I have a 1982 car.
The A/c does not work. I took it for a country run yesterday about 30mins (I live in the country – so getting to high speed roads (100km…not exactly high speed). Then came home, turned the throttle screw and basically nothing happened. In park the car idles at about 400rpm. The red changing light does not appear – so that is good.

D
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1983 AU Car Idle speed 15 Sep 2019 00:39 #20965


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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.
Rich
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Last Edit: 15 Sep 2019 00:39 by Rich928.
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