Idle Speed Control System - Operation and Testing
84VW03Applies To RABBIT, JETTA 1.7
with engine code EN
GTI, CONV., GLI, SCIROCCO 1.8 with engine code JH
1984 model year
Group 25
Subject
1.7, 1.8 Engines
Part Identifier N/A
Key Points
Idle speed boost valves Air shrouded injectors Altitude compensated warm up regulator A-075
Number
84-01
February 27, 1984
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 illustration)
- 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 illustration)
- 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
^ 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
^ both the warm-up regulator and auxiliary air regulator must have proper electrical connection
^ warm-up regulator temperature at least 20~C (68~F)
Wiring Diagram