Idle Speed: Adjustments
Idle Speed (duty Cycle) And CO Value Must Be Checked And Adjusted TogetherTEST CONDITIONS
- engine oil temperature min. 80°C (176°F)
- all electrical consumers switched OFF (A/C and radiator cooling fan must be OFF)
- pressure gauge not connected
- exhaust system must be free of leaks
- it injection system has been opened or components replaced, run engine several times to 3,000 rpm for approx. two minutes before starting this procedure
- disconnect crankcase ventilation hoses and seal off openings (arrows)
- remove charcoal cannister hose from intake air boot connector (arrow) and leave open
NOTE: Intake air boot hose connector has calibrated orifice and must remain in opening.
- remove harness connector from differential pressure regulator
- attach test adaptor vw 1315A/1 between unplugged harness connector and differential pressure regulator
- attach US 1119 to test adaptor VW 1315A/1
- switch US 1119 to DCA 200 mA range
- remove cap from CO probe receptacle
- connect CO test hose to probe receptacle (arrow)
^ hose must fit snug so there is no exhaust leak
- connect tester VW 1367 using cable adapter US 1112
- push % button on VW 1367
- start engine and run at idle
- check idle speed (duty cycle) with VW 1367
- checking value 28 ± 2% (with oxygen sensor connected)
If NO
- correct duty cycle with idle adjustment screw (arrow)
- adjusting value 28 ± 1% (with oxygen sensor unplugged)
If OK
- check rpm display on VW 1367
- must be 800 ± 50 rpm
NOTE: Idle speed is controlled by idle stabilizer valve. Only duty cycle is adjustable.
If NO rpm value is displayed on VW 1367
- check idle stabilizer
If rpm value OK
- unplug oxygen sensor connector
- check CO value
- checking value 0.3 - 3.0%
If NO
- turn OFF ignition
- remove intake air boot from mixture control unit
- center punch mixture adjusting screw plug
- drill 2.5 mm (3/32 in.) hole in center of plug 3.5 - 4.0 mm (9/64 - 5/32 in.) deep
CAUTION: Clean up any metal shavings. Apply grease to drill bit to catch any shavings.
- screw in 3 mm (1/8 in.) sheet metal screw
- remove plug with screw, using pliers
- start engine and run at idle
- adjust CO by turning mixture adjusting screw with tool P377
- adjusting value 0.6 - 1.0%
CAUTION: When adjusting do NOT push adjustment wrench down or accelerate engine with adjusting tool in place. Remove tool after each adjustment and briefly accelerate engine before reading CO value.
If CO value OK
- read differential pressure regulator current displayed on meter US 1119
- current must correspond to above chart
^ Example: 1,000 ft above sea level should be approx. 8 - 12mA
If current NOT OK
- check altitude sensor
If current OK
- reconnect oxygen sensor
- recheck duty cycle
- duty cycle must remain within checking value of 28 ± 2%
- read current displayed on meter US 1119
- displayed current must fluctuate
If current DOES NOT fluctuate
- Check oxygen sensor
If current fluctuates
- turn ignition OFF
- reconnect crankcase ventilation and charcoal cannister hoses
- drive in new plug flush with mixture control unit
- remove CO meter and reattach cap to CO probe receptacle