Minimum Air Rate - Fuel Injection Only

Minimum Idle Speed Screw:

These adjustments should be performed only when throttle body parts have been replaced or when required to do so by the TPS adjustment. The engine should be at normal operating temperature before making all adjustments.
The minimum idle speed screw used to regulate the minimum idle speed of the engine, is pre-adjusted at the factory. The speed screw is covered with a plug to discourage unnecessary adjustment. If it is necessary to adjust the minimum idle speed screw, pierce the plug with an awl and apply leverage to remove it.

PRELIMINARY CHECKS:

1. Enter diagnostics and record all trouble codes displayed. If current or history codes are found, refer to COMPUTERIZED ENGINE CONTROLS/DIAGNOSIS AND TESTING PROCEDURES/TESTING PROCEDURES/DIAGNOSTIC CHARTS/TROUBLE CODES.
2. Perform PFI system check, refer to COMPUTERIZED ENGINE CONTROLS/DIAGNOSTIC AND TESTING PROCEDURES. If the chart leads to "Fuel System is controlling," proceed to step 3.
3. START the engine. Enter Diagnostics. Select PCM data ED04, "Coolant Temperature". Operate the engine until coolant temperature is greater than 95°C.
4. Perform the PCM input tests EI72 and EI74. Refer to the appropriate trouble trees in COMPUTERIZED ENGINE CONTROLS for diagnosis of inputs that do not cycle. If both inputs cycle, proceed to step 5.
5. EXIT DIAGNOSTICS. Select the OFF mode on the CCDIC (this will turn the A/C compressor off). Wait ten seconds. START the engine and reenter diagnostics. Place the steering wheel in the center, straight ahead position. Transmission should be in PARK.
6. Enter set timing mode by jumpering Pin A to Pin B of the ALDL connector. The CCDIC will display the "Set Timing" message with the jumper in place. If the "Set Timing message does not appear, refer to COMPUTERIZED ENGINE CONTROLS. Check for timing at 10° BTDC and adjust as necessary. Disconnect the jumper at the ALDL after the timing is verified as correct. Reinstall the connector cover and verify that the cover is latched.
7. Visually check all vacuum hoses for splits, leaks or cuts. Repair as required.

CHECKING MINIMUM IDLE SPEED:

8. Select PCM override ES03 "ISC Motor".
9. Press the "Cooler" button on the CCDIC to retract the ISC motor. This action will disengage the A/C compressor, disable the generator and provide a steady spark advance to the engine. The ISC motor will slowly retract (about 20 seconds) to a fully retracted position. Verify that the throttle lever is resting on the minimum idle speed screw. If the engine stalls at this point, go to step 12.
10. With the ISC fully retracted, the plunger should not be touching the throttle lever. The throttle lever must be resting on the minimum air screw. If contact is noted, adjust the ISC plunger (turn in) with pliers or available special tool J 29607 so that it is not touching the throttle lever. Make sure that the throttle is not being bound by the throttle, cruise or TV cables.
11. Check the minimum idle speed using PCM data parameter ED11, "Engine rpm". If the minimum idle speed is outside of the following limits, proceed to step 12. Use an average reading of rpm to check minimum idle rpm.
^ For Vehicles With 0-500 Odometer Miles:
Minimum idle rpm should be 425-525 rpm.
^ For Vehicle With More than 500 Odometer Miles:
Minimum idle rpm should be 500-600 rpm.
If minimum idle speed is OK, go to step 14.
12. If the engine stalled at minimum air (ISC fully retracted), check the primary throttle blades for deposits that might restrict air flow. If there are deposits, clean the primary throttle bore and the area behind and around the throttle plate using a clean shop towel with top engine cleaner or equivalent. DO NOT USE ANY SOLVENT THAT CONTAINS METHYL ETHYL KETONE. Return to Step 8 after cleaning the throttle body.

IF ADJUSTMENT IS REQUIRED:

NOTE: If the engine speed is not within the above limits (too high), check for vacuum leaks at the throttle body, intake manifold, vacuum fittings, tees and hoses. If the minimum air setting is made with a vacuum leak present, fuel control can be adversely affected throughout all driving ranges.

13. If the minimum idle speed is out of limits, adjust the minimum idle screw to obtain the following idle speed:
^ For Vehicles With 0-500 Odometer Miles:
Set minimum idle rpm to 475 rpm.
^ For Vehicle With More than 500 Odometer Miles:
Set minimum idle rpm to 550 rpm.
Use a T-20 torx driver to adjust the minimum idle speed screw. If the idle speed cannot be corrected, check that the throttle is not held off minimum idle speed screw because of linkage binding or interference with the ISC plunger. Also, check vacuum hoses for leaks and check for air leaks at the throttle body mounting and intake manifold. After adjusting the minimum idle speed, proceed to Step 14.

TPS SETTING CHECK:

14. With the engine running, select PCM override ES03, "ISC mother", and press the "Cooler" button (retract ISC motor). Select PCM data ED01, "TPS", while still in PCM override ES03. Note the throttle position (in degrees) displayed on PCM parameter ED01:
^ -1.0° to +1.0°
Go to step 17
^ TPS -10.0° to -1.1° to TPS +1.1° to +90.0°
Go to step 15.

TPS ADJUSTMENT:

15. If the throttle angle displayed is outside the -1.0° to +1.0° band, the TPS sensor needs to be adjusted. This adjustment will be performed by using the TPS parameter in diagnostics.
16. Using a torx-25 driver, loosen the TPS screws just enough to permit the sensor to be rotated. Open the throttle and allow the throttle lever to snap shut against the minimum air screw. Adjust the TPS so the parameter display is -.5° to +.5°. Go to step 17, "Maximum ISC Extension Adjustment".
CAUTION: DO NOT use excessive force (don't pry or pound) to adjust the TPS or damage to the TPS may occur. The TPS mounting screw must be loosened to perform the adjustment.

ISC MAXIMUM EXTENSION CHECK AND ADJUSTMENT:

17. With the key ON, select the ISC motor override ES03. Press the "WARMER" button on the CCDIC. The display should change from "50" to "99" indicating that the override function has started. The ISC will extend to the maximum extend position.
18. With the ISC at maximum extension the TPS parameter, ED01, should be between 13.4 and 15.8. If the parameter is not within this range, adjust the ISC plunger as follows:
^ TPS below 13.4 degrees
^ Adjust the ISC plunger out by turning the plunger counterclockwise until the TPS parameter reads 15.0.
^ TPS above 15.8 degrees
^ Adjust the ISC plunger in by turning the plunger clockwise until the TPS parameter reads 15.0.

AFTER ALL CHECKS AND ADJUSTMENTS ARE COMPLETED:

19. Exit diagnostics. Allow approximately 20 seconds for the ISC motor to close to a pre-start setting.
20. Turn the ignition key OFF for a minimum of 10 seconds to allow the PCM to complete a TPS Learning routine.
21. START the engine and check for proper ISC motor operation.