Firebird V8-305 5.0L VIN E (1992)
Idle Speed: Adjustments
Minimum Air Rate - Fuel Injection Only
NOTE: The minimum idle air rate is set at the factory with a stop screw and is not normally readjusted unless repairs or replacement of the throttle body
assembly has occurred.
CONTROLLED IDLE SPEED CHECK
1.
Set parking brake and block drive wheels.
2.
Connect a SCAN tool to the assembly line data link (ALDL) connect with tool in Open Mode.
3.
START engine and bring it to normal operating temperature.
4.
Check for correct state of PARK/NEUTRAL switch on SCAN tool.
5.
Check specifications chart for controlled idle speed and IAC valve pintle position (counts).
6.
If within specifications, the idle speed is being correctly controlled by the ECM.
7.
If not within specifications, perform MINIMUM IDLE AIR RATE CHECK. If still not within specifications refer to DIAGNOSIS, TESTING
AND INSPECTION PROCEDURES.
MINIMUM IDLE AIR RATE CHECK
1.
Check controlled idle speed and perform idle air control check first.
2.
Set parking brake and block drive wheels.
3.
START engine and bring it to normal operating temperatures 185-212 degrees Fahrenheit (85-100 degrees Celsius). Turn engine OFF.
4.
Remove air cleaner, adapter and gaskets. Check that the throttle lever is not being bound by the throttle, throttle valve or cruise control cables.
5.
With IAC valve connected, ground the diagnostic terminal (ALDL).
6.
Turn ON ignition, DO NOT START engine. Wait at least 10 seconds (this will allow the IAC pintle to extend and seat in the throttle body).
7.
With ignition ON, engine stopped, test terminal still grounded, disconnect IAC valve electrical connector. (This disables the IAC valve in the
seated position). Remove the ground from the diagnostic terminal.
8.
Connect a SCAN tool to the ALDL connector and place in open mode. If a tool is not available connect a tachometer to the engine.
9.
START engine. With transmission in NEUTRAL, allow engine rpm to stabilize.
10.
Check rpm against specifications. Disregard IAC counts on SCAN tool with the IAC disconnected. If the engine has less than 500 miles or is
checked at altitudes above 1500 feet, the idle rpm with a seated IAC valve should be lower than values in chart below.
11.
If the minimum idle air rate is within specifications, no further check is required.
12.
If the minimum idle air rate is not within specifications, perform the following procedures:
13.
If soft plug is present, remove the stop screw plug by piercing it with an awl, then applying leverage. The screw is covered to discourage
unauthorized adjustments.
Stop Screw Plug Removal
14.
With the engine at normal operating temperature 185-212 degrees Fahrenheit (85-100 degrees Celsius), adjust stop screw to obtain nominal rpm
per specifications with seated IAC valve.
15.
Turn ignition OFF and reconnect IAC valve electrical connector.
16.
Disconnect the SCAN tool or tachometer.
17.
Reset the IAC motor by depressing accelerator slightly and starting engine. Run engine for 5 seconds then turn engine off for 10 seconds. Restart
and check for proper idle operation.
18.
Use silicon sealant or equivalent to cover stop screw hole.
19.
Install air cleaner, adapter and gasket.
CONTROLLED IDLE SPEED
Transmission
Gear
Idle Speed
IAC Counts [1]
OPEN/CLOSED Loop [2]
Auto
D
preferred +/- 50
5-50
CL
Auto
N
preferred +/- 100
5-50
CL
[1] Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).
