1.7L/1.8L - Idle Speed Boost Valve Function/Checking (GROUP 25, NO. 84-01)

WARNING: This page is about the Rabbit L, 2D Hatchback, 1.6 G, Automatic, which is a different variant/trim than selected.

Publication date: 1984-02-27
Reference number: GROUP 25, NO. 84-01

1.7L/1.8L - IDLE SPEED BOOST VALVE FUNCTION/CHECKING

TECHNICAL SERVICE BULLETIN

Reference Number(s): GROUP 25, NO. 84-01

1.7, 1.8 ENGINES - IDLE SPEED BOOST VALVES - AIR SHROUDED INJECTORS- ALTITUDE COMPENSATED WARM UP REGULATOR

Model(s): 1984 Volkswagen Rabbit, Jetta 1.7 (engine code EN)

GTI, Conv., GLI, Scirocco 1.8 (engine code JH)

Group: 25 - Continuous Fuel Injection

Bulletin No.: 84-01

Part Identifier: N/A

Date: February 27, 1984

IDLE SPEED BOOST VALVES

Refer to Fig 1 .

Idle Speed Boost Valve #1 (black)

On all vehicles.

Idle Speed Boost Valve #2 (white)

Additional valve for A/C equipped vehicles.

IDLE BOOST VALVE #1, FUNCTION

Instead of the electronic stabilizer, idle boost valve #1 regulates idle.

With ignition ON, voltage is supplied to boost valve #1.

If engine speed drops below 700 RPM, the idle boost control unit completes the ground circuit to boost valve # 1. This raises idle speed.

NOTE: Idle boost control unit located on fuse/relay panel, relay location No. 16.

If engine speed above 1050 RPM, control unit opens ground circuit to boost valve #1.

GROUNDING CIRCUITS

If ground circuit complete, valve #1 is open (idle increases).

If ground circuit open, valve #1 is closed (idle not increasing).

IDLE SPEED BOOST VALVE #1, CHECKING

A/C switched OFF.
Engine oil temp. at least 80°C (176°F).

- Connect tachometer to engine.

- Pinch off hose #3 (in location shown in Fig 1 .).

- Disconnect oxygen sensor at electrical connection.

- Run engine at idle speed.

- Adjust idle speed to less than 700 RPM.

Valve # 1 should be heard to "click" on.

- Remove pinch clamp from hose 3.

- Idle RPM should increase slightly.

- Briefly raise idle speed above 1100 RPM.

Valve #1 should be heard to "click" off.

- Reconnect oxygen sensor connector.

- Pinch off hose #3 (in location shown in Fig. Fig 1 ).

- Adjust idle speed to 925 +/- 25 RPM.

NOTE: Hose #3 must be pinched off during idle speed checking/ adjusting procedure.

NOTE: On engines equipped with air shrouded injectors, test boost valve #1 by pinching off fuel injector air feed hose to lower idle RPM.

IDLE BOOST VALVE #2, FUNCTION

Valve #2 is constantly grounded. Voltage is supplied to boost valve #2 when A/C is switched on.

A/C switched ON, valve #2 is OPEN (RPM increasing).
A/C switched OFF, valve #2 is CLOSED (RPM not increasing).

IDLE BOOST VALVE #2, CHECKING

A/C switched OFF.

- Run engine at idle speed.

- Pinch off hose #3.

RPM must not change.

- Switch ON A/C.

- Engine at idle speed and #3 pinched off. See Fig 1 .

RPM must decrease.

CAUTION: Note installation position of idle boost valve T-fitting. Connection with larger opening must be attached to boost valve #2.

AIR SHROUDED FUEL INJECTORS (1.8 ENGINE ONLY)

Air shrouded injectors allow lower idle speeds and a leaner fuel mixture due to better fuel atomization.

Special injector inserts are used as well as injectors with tighter manufacturing tolerances.

New injector Part Number: 049 133 551A

The new injectors can be used in earlier vehicles without air shrouding, however the inserts cannot.

WARM-UP REGULATOR WITH ALTITUDE COMPENSATION

1.7 USA (except California and Canada)

1.8 All

NOTE: It is important to know the altitude of the workshop vicinity where the vehicle is to be checked.

CONTROL PRESSURE SPECIFICATIONS - ENGINE WARM

Refer to Fig 2 .

Both the warm-up regulator and auxiliary air regulator must have proper electrical connection.
Warm-up regulator temperature at least 20°C (68°F).

Fig 1: Idle Speed Boost Valves

Fig 2: Control Pressure Specifications