C 2500 Truck 2WD V8-305 5.0L (1990)
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.
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:
Stop Screw Plug Removal
13.
If present, remove the stop screw plug by piercing it with an awl, then applying leverage. The screw is covered to discourage unauthorized
adjustments.
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.
Use silicon sealant or equivalent to cover stop screw hole.
18.
Install air cleaner, adapter and gasket.
CONTROLLED IDLE SPEED
Transmission
Gear
Idle Speed
IAC Counts [1]
OPEN/CLOSED Loop [2]
Man.
N
600
5-30
OL
Auto
D
500
5-30
OL
Auto*
D
500
5-30
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).
[*] 3 Speed Auto in a C1500 Pickup w/federal emissions (NA5) and no AIR system.
MINIMUM IDLE AIR RATE
Transmission
Gear
Engine Speed
OPEN/CLOSED Loop [1]
Man.
N
500 +/- 25
OL
Auto.
D
425 +/- 25
CL
[1] Let engine idle until proper fuel control status (OPEN/CLOSED loop) is reached.
