CO (Mixture) Checking/Adjusting
Group: 24Number: 92-03
Date: 02/20/92
Subject:
Checking/Adjusting Basic Setting Using VAG 1551 scan tool
Model(s):
100 All M.Y. 1992
Requirements:
- minimum engine coolant temperature 85°C (185°F)
- all electric consumers switched off
- air conditioner switched off
- climate control switched off (CS model) repeatedly press minus button for blower speed selection in A/C control head until all displays are erased
- transmission selector lever in P or N
- disconnect crankcase ventilation hoses from valve covers and plug both hoses with suitable piece of round stock
- connect the VAG 1551 scan tool to the appropriate connectors in the auxiliary relay station underneath the hood
- start the engine and let idle
Display will appear as shown
Note:
A list of possible functions will be printed after pressing the Help button
- press 0 and 1 buttons to select address word 01 "engine electronics"
Display will appear as shown
- press Q button to enter input
Display will appear as shown
- press --> button
- watch channel 8 (oxygen sensor control; avg. of both cyl. banks): display value should average around 128
Note:
For an explanation of the various channel displays, --> D2-40-4
If channel 8 display value is outside specification:
- remove CO adjustment screw cap (arrow) at air mass sensor housing and pry out plastic plug or drill it out if metal plug is used
- adjust CO content to display 128 by turning CO adjusting screw during basic setting
Note:
The display value does not change immediately after turning the CO adjusting screw. There will be a slight delay.
- connect CO tester Sun 105: (or equivalent) to CO tap tube on right
- read CO content must be 0.3 - 1.2% by volume
- repeat CO content test on left CO tap tube
If CO content is less than 0.3% by volume (even though value displayed on VAG 1551 is correct):
- eliminate leak in area of CO tap tube or adapter cable
If CO content is more than 1.2% by volume:
- eliminate leak in exhaust system between engine and oxygen sensor
- install new plug over CO adjusting screw
- press on cap
when values are displayed in all channels
- press --> button