OXS Duty Cycle & Emission Control Information
OXS duty cycle for duty cycle valve and CO content, checkingChecking specifications:
^ OXS duty cycle 20-70% reading must fluctuate
^ CO-content 0.3-1.2%
Note
If the CO content is more than 1.2% by volume at an OXS duty cycle reading of 20-70%, this is not caused by incorrect CO adjustment.
Possible Causes
^ ignition system not OK
^ leak in exhaust system
^ fuel injector seats loose or leaking
^ fuel distributor defective (different injection quantities between cylinders at idle)
If the OXS duty cycle reading is less than 20% or greater than 70%, adjust OXS duty cycle to adjusting specifications with the CO adjusting screw as follows:
- remove boot on mixture control unit
- center punch mixture adjusting screw plug
- drill 2.5 mm (3/32 in.) hole in center of plug 3.5-40 mm (9/64-5/32 in.) deep
CAUTION
Clean up any metal shavings. Apply grease to drill bit to catch shavings.
- screw in 3 mm (1/8 in.) sheet-metal screw
- remove plug with screw, using pliers
- start engine and run at idle
- adjust OXS duty cycle with CO adjusting screw (6)
^ adjusting specification: 50 +/- 8%
^ reading MUST fluctuate
CAUTION
When adjusting, do not push adjustment wrench down. Do not accelerate engine with tool in place. Remove tool after each adjustment and accelerate engine briefly before reading meter.
- correct idle speed if necessary
Note
After adjusting the idle, the crankcase breather hoses have to be reconnected. If the OXS duty cycle reading and CO content change when they are reconnected, it is not caused by incorrect adjustment, but because of oil thinning due to excessive short distance driving. Longer, high speed driving, with minimal stop and go, will decrease the amount of fuel in the oil, resulting in increased stabilization of OXS duty cycle and CO content. The condition can be temporarily corrected by changing the oil.
FIGURE 1 - CONTROL UNIT/OXYGEN SENSOR:
Emission control components
^ control unit location - Fig. 1 checking - Page 6
^ oxygen sensor location - Fig. 1 checking - Page 7
FIGURE 2 - RELAY LOCATIONS (GOLF):
FIGURE 3 - RELAY LOCATIONS (JETTA):
^ relay locations - Figs. 2 and 3
FIGURE 4 - THERMOSWITCH LOCATION (A):
^ thermoswitch location and checking - Fig. 4
^ duty cycle valve location and checking - Page 5
^ catalytic converter same as CIS-E engines
FIGURE 1 - CONTROL UNIT/OXYGEN SENSOR:
Control unit (1) is installed in the left side of the plenum. The oxygen sensor (2) is positioned in the exhaust manifold.
FIGURE 3 - RELAY LOCATIONS (JETTA):
2 - fuel pump relay 15 - power supply relay for Lambda control 16 - idle speed stabilization relay
- check resistance on contacts specified value: over 28~C (82~F) (infinite) ohms under 15~C (59~F) 0.0 ohms
If NO
- replace thermoswitch
Emission controls, checking (With engine not running) Connecting test equipment
CAUTION
Inductive pickup (on VW 1367) must NOT be connected.
- remove connector (2) of auxiliary air regulator (1) and connect it to connector (3) of the remote control US 4480/3 -connect alligator clip (4) to battery (+)