Idle Speed Control Check
- Start engine. If engine will not start go to step 4). With engine running listen for operation of vacuum control modulator. If vacuum modulator is working properly allow engine to warm up. If control modulator is not working properly, replace vacuum control modulator and begin at start of step 1). Turn diagnosis start switch to "ON" position.
- Disconnect coolant temperature sensor harness connector. Connect a jumper wire between 2 terminals of connector. Check vacuum reading between vacuum control modulator and idle speed control actuator. Vacuum reading should be 2.5-4.0 in. Hg. After checking vacuum, stop engine and turn diagnosis start switch to "OFF" position.
- Reconnect coolant temperature sensor connector. If vacuum reading is not as specified, check air filters and vacuum piping for clogs. See Fig 1 . If vacuum is as specified, see IMPROPER IDLE, ENGINE STATABILITY and ENGINE STALL DIAGNOSTIC CHART procedures.
- Apply about 8 in. Hg to vacuum control modulator input connector. Set vacuum gauge between control modulator and idle speed control actuator. Apply 12 volts to terminals of vacuum control modulator. Vacuum should read 1-2 in. Hg.
- If vacuum reading is not as specified replace vacuum control modulator. If vacuum reading is as specified and idling speed control system still does not operate properly, see IMPROPER IDLE, ENGINE STATABILITY and ENGINE STALL DIAGNOSTIC CHARTS.