Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1989R 20 P/U 2WD L6-292 4.8LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSADJUSTMENTS
1989 Chevrolet R 20 P/U 2WD L6-292 4.8L
Computers and Control Systems: Adjustments
1989 Chevrolet R 20 P/U 2WD L6-292 4.8LSECTION Adjustments
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.
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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.