V 3500 P/U 4WD V8-454 7.4L VIN W 4-bbl (1988)
Idle Speed: Adjustments
Idle Speed
Carbureted
Disconnect and plug hoses as indicated on emission label.
Adjust idle to specified rpm by adjusting idle solenoid screw (plunger fully extended) or throttle stop screw.
Air-conditioned models equipped with idle speed-up solenoid, turn AC on, disconnect compressor clutch wire with solenoid fully extended, adjust
solenoid to obtain specified rpm. Turn air conditioner off and reconnect compressor wire.
Electrically disconnect idle shutdown solenoid, if so equipped, and adjust idle speed screw or solenoid hex-head screw to obtain SHUTDOWN IDLE
SPEED of 450 rpm, unless specified otherwise. Reconnect solenoid lead.
Reconnect hoses, unless specified otherwise on label. On models equipped with CEC solenoid, disconnect electrical lead.
Set fast idle to specified rpm with transmission in NEUTRAL or PARK, unless otherwise specified.
Fuel Injection
*** UPDATED BY TSB # 88T556E DATED NOV. 1987
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 Computers and Control
Systems / Testing and Inspection / Procedures / Diagnosis By Symptom.
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.
