Adjusting idle speed

Identification: Information plate in national language on cross member in front of radiator or on cylinder head cover. Adjust engines according to data of respective emission control information plate.

National version

Idle speed 1/min

Idle speed emission value % CO

up to 1976

max. 1.5

1976

800-900

max. 1.0 without air injection

1976

1973

750-900

up to 1.5

(us*) 1974 Federal

1974 California

700-900

6—8 without air injection

1975/76

800-900

max. 1.0 without air injection

National version

Engine speed

Vacuum hose pulled off

1/min

Engine speed

Driving position engaged

1/min

TN choke

TN choke

1976

1976

1700-1900

600-700

(usa) 1973/74

1200-1400

1975/76

‘) When engaging all auxiliary units, the engine should still run smoothly.

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Oil telethermometer

116 589 27 21 00

Digital tester

001 589 54 21 00

Connecting cabie 6 m long

000 589 04 90 00

Intermediate plug (adaptor)

000 589 72 63 00

Trigger

000 589 71 63 00

Rpm and CO measuring instrument

Do not set idle speed on dynamometer when the engine is too hot, e.g. immediately after a fast drive or after measuring output. The air filter must be mounted.

1    Connect test instruments:

•   digital tester or revolution counter

•   CO measuring instrument

•   oil telethermometer

2   Switch off air conditioning system or automatic climate control. Move selector lever into position “?”.

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3   Check whether on vehicles with cruise control (Tempomat) the Bowden wire rests free of tension against regulating lever. Adjust Bowden wire with adjusting nut (1), if required. For this purpose, run engine.

4   Set engine oil temperature to 60—80 °C.

5   Check intake system for leaks. For this purpose, spray all sealed points with Iso-Oktan DIN 51 756 or benzine. A changing engine speed or CO value indi­cates the presence of leaks.

Do not use conventional fuel for spraying (unhealthy vapors). Pay attention to inflammability and do not spray on the red-hot parts or components of the igni­tion system.

6   With the engine running, check whether throttle valve lever (3) rests against adjusting screw (68).

7   Check idle speed and adjust with adjusting screw (68), if required.

8 Check idle speed emission value without air injec­tion. For this purpose, make air injection inoperative as follows (for (@) 1973/74 nothing need be made inoperative):

Pull off blue/purple vacuum line at connecting point (arrow).

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Pull rubber cap (arrow) from blue/purple vacuum line.

j[) 1976, model 116

Pull rubber cap (arrow) from blue/purple vacuum line.

(us*) California 1974

Pull off red vacuum line at connecting point (arrow). @) 1975/76

Pull off blue/purple vacuum line at connecting point (arrow).

The exhaust gas for idle speed CO measurement on vehicles with catalyst, (T) 1976 and (usa) 1975/76, is drawn off in front of catalyst at check valve (arrow) of air injection.

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For measuring idle speed emissions, open valve plate of check valve by means of a self-made wire hook. Connect exhaust gas hose of CO measuring instrument to check valve.

9 Adjust idle speed emission value without air injec­tion. For this purpose, adjust both adjusting screws (arrows) uniformly.

Accelerate for a short moment, check idle speed and idle speed emission value once again and readjust, if required.

10    Reattach vacuum hose for air injection (air injec­tion operating). The idle speed emission value should now be below the previously set value.

11    Adjust vacuum governor. Run engine, pull off vacuum hose (64), set to specified speed by means of an adjusting screw (63), attach vacuum hose.

When loosening counternut, apply counterhold to diaphragm rod.

Engage driving position on automatic transmission, set to specified speed by means of adjusting nut (61). Turn power steering to full lock and engage air condi­tioning system, engine should still run smoothly. Readjust speed, if required.

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