Mitsubishi 3000GT Service Manual page 78

ENGINE
IDLE MIXTURE CHECK
(1) Before inspection, set the vehicle in the following condi-
tion.
Engine coolant temperature: 80-95°C (176-203°F)
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Lights, electric cooling fan and accessories: OFF
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Transaxle: P range
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(2) Make sure that the basic ignition timing is of a standard
value.
Standard value:
(3) After turning the ignition switch OFF, set a tachometer
or connect the scan tool to the data link connector.
NOTE
For tachometer setting procedure, refer to P.ll -9.
(4) Start the engine and run at 2,500 rpm for approx. 2 min-
utes.
(5) Set the CO tester and HC tester.
(6) Check the CO concentration and HC concentration with
the engine at idle.
Standard value:
CO concentration: 0.5 % or less
HC concentration: 100 ppm or less
(7) If the standard value is exceeded, check the following
items.
Diagnostic output
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Closed loop control (if closed loop control is performed
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normally, heated oxygen sensor output signals
change within a O-400 mV range and a 600-l ,000
Fuel pressure
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Ignition coil, spark plug cables and spark plugs
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Leaks in EGR svstem and EGR valve
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Evaporative emission control system
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NOTE
If CO and HC concentrations exceed the respective stan-
dard values despite the fact that the results of the inspec-
tion made on all items are normal, replace the three-way
catalyst.