Idle Speed: Testing and Inspection

TEST CONDITIONS
- engine oil temperature minimum 80°C (176°F)
- ignition timing OK
- A/C switched OFF

WORK SEQUENCE





- connect tester VW 1367 using cable adapter US 1112
- push % button on VW 1367
- check duty cycle
- specification: 28 ± 12% (with oxygen sensor connected)

If NO
- adjust duty cycle If still NOT OK, and duty cycle reading is 33% or 40%
- check that A/C is switched OFF

If A/C OFF
- check idle switch for function or for open circuit between idle switch and control unit connector

If cycle reading fluctuates irregularly between 25% and 20%
- check for open rpm signal circuit from electronic ignition control unit

If duty cycle reading is 25%
- idle speed incorrect
- check for leaks at throttle body gaskets and seals

If NO leaks present
- check for open circuit between idle stabilizer and control valve.

If circuit OK
- replace control valve

A/C SWITCH SIGNAL, CHECKING
- switch A/C ON
^ rpm boost approximately 100 rpm

If NO
^ check for open circuit between dash switch and control unit connector terminals 6 and 16

A/C COMPRESSOR SIGNAL, CHECKING
- switch A/C ON
- A/C compressor has switched OFF
^ rpm boost approximately 100 rpm

If idle increases over 1,000 rpm with A/C compressor OFF
- voltage signal wire from compressor to control unit connector terminal 19 interchanged with terminal 16. Correcting