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 MANUALSCHEVROLET1985STEP VAN P20, 6.2 J, AUTOMATIC, 475/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEADJUSTMENTTUNE-UP - V8ADJUSTMENTSBEST IDLE PROCEDUREHEAVY DUTY MODELS ONLY
1985 Chevrolet Step Van P20, 6.2 J, Automatic, 475/M40
Heavy Duty Models Only
1985 Chevrolet Step Van P20, 6.2 J, Automatic, 475/M40SECTION Heavy Duty Models Only
- Set parking brake and block drive wheels. Warm engine to normal operating temperature. Remove air cleaner. Place transmission in Neutral and connect tachometer.
- Turn idle mixture screws in lightly to seat them, then back out 2 turns. Do not turn screws tightly against seat or damage may result.
- With engine running, choke open, and transmission in Neutral, adjust idle speed to specification. Adjust mixture screws to obtain maximum RPM.
- Readjust idle speed screw to specification, and readjust mixture screws to obtain highest RPM. Turn ignition off, and install air cleaner.
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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.