Minimum Air RPM Check
Preliminary Checks1. Enter diagnostics and record all trouble codes displayed. If current or history codes are found, see "Diagnosis Procedures" in Section 8D. When all trouble codes are repaired, proceed to step 2.
2. Perform PFI system check in Section 6E, sub-section A. If the chart leads to "Fuel System is Controlling", proceed to step 3.
3. Start the engine. Enter diagnostics. Select ECM data ED04 "Coolant Temperature". Operate the engine until coolant temperature is greater than 85~C.
4. Perform ECM input test E172 and E174. Refer to the trouble tree in Section 8D1 for diagnosis if input does not cycle. If both inputs cycle, proceed to step 5.
5. Exit diagnostics. Select the "OFF" mode on the CCDIC. Wait 10 seconds, then reenter diagnostics. Place the steering wheel in its center position. Place the transmission in park.
6. Enter set timing mode by jumpering Pin A to B of the ALDL connector. Check for timing at 10 degrees BTDC and adjust as necessary. Disconnect the jumper at the ALDL and reinstall the connector cover. Ensure that the cover is latched.
7. Visually check all vacuum hoses for splits, leaks, or cuts and assure that there are no vacuum leaks.
8. Enter diagnostics and select ECM override ES03 "ISC motor".
9. Press the cooler button to retract the ISC motor. When fully retracted, check minimum air idle RPM.
Figure 4 - Removing Idle Stop Screw Plug:
10. Minimum idle RPM should be:
^ 450-550 if odometer is less than 500 miles
^ 450-600 if odometer is greater than 500 miles
If the minimum idle speed is out of these RPM limits, connect a tachometer to the engine and adjust the minimum idle speed screw to 500 rpm. Remove and discard the minimum idle speed screw plug. Use a T-20 torx driver to adjust the minimum idle speed screw. If the engine speed cannot be corrected, check that the throttle is not held off the minimum idle speed screw because of linkage binding or interference with the ISC motor plunger. Also check vacuum hoses for leaks, for air leaks at throttle body mounting and intake manifold. After adjusting minimum idle speed, proceed to TPS adjustment procedure.