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.
ROCHESTER 4GC 4-Barrel: Adjustment: Notes
IDLE SETTING CAUTION (CARS WITH HOT IDLE COMPENSATOR) - Make sure that idle compensator is closed when adjusting idle speed. If necessary, idle compensator valve can be closed manually. After idle speed is adjusted, press down on idle compensator to see if speed is affected. If speed drops, readjust idle speed, being sure that hot idle compensator valve is closed.
BUICK NOTE - Transmission idle stator switch must be closed when making idle adjustment. Check by disconnecting switch connector. If idle speed does not decrease, switch was not closed. Adjust switch and readjust idle speed and mixture.
CADILLAC NOTE - On cars with Automatic Level Control, disconnect vacuum hose to level control compressor and tape hose "T" fitting when making idle adjustment. If this is not done, idle performance will be unsatisfactory when compressor is not operating.
CHEVROLET NOTE - On cars with Automatic Level Control, idle adjustment must be made exactly as follows to prevent rough idle when compressor operating: Adjust level control reservoir pressure to 70 lbs. (use Shrader valve on compressor), adjust idle mixture with compressor operating, then with compressor off (crimp hose or disconnect hose and block vacuum source), check idle speed and adjust as necessary, finally readjust idle mixture for best compromise between compressor operating and compressor not operating conditions.
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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.
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