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 MANUALSCHEVROLET1985IMPALA 4.3 Z, 700R4/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMFEEDBACK CARBURETOR TESTS W/CODESCHART A1 - DWELL FIXED UNDER 10°
1985 Chevrolet Impala 4.3 Z, 700R4/MD8
Chart A1 - Dwell Fixed Under 10°
1985 Chevrolet Impala 4.3 Z, 700R4/MD8SECTION Chart A1 - Dwell Fixed Under 10°
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- 1) This test determines if problem is CCC or engine related. Dwell should start increasing as soon as engine is choked and increase until it is over 50°. If dwell responds, problem is lean engine.
- 1A) This checks for causes of lean condition that resulted in full rich command.
- 2) This test checks for ECM response to input to O2 sensor circuit. The voltmeter is used to put a voltage on the O2 sensor circuit to simulate a rich condition. Dwell should increase (a lean command) if ECM and harness are good.
- 3) This test checks for normal coolant sensor circuit condition. Voltage on a normalized hot engine should be under 2.5 volts.
- 4) This step checks for an open in the ground circuit to ECM term. "14" and grounded O2 sensor circuit. Terminal "2" voltage should be under 1.0 volt at idle. A high voltage could be caused by an open in the circuit at term. "22". Normally this will cause Codes 21 and 34 (and 35 if equipped with idle speed control) but won't set them on some engines.
RENDER: 1.0x
NO RELATED
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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.