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.
1980 Plymouth Champ Custom, Automatic TransFACTORY OEM SERVICE PROCEDURE
Combustion Computer Test
- Connect tachometer to engine. Start engine and warm to operating temperature. Disconnect coolant temperature switch and CTS switch (if equipped). DO NOT ground carburetor switch.
- Set engine speed at 1200 RPM. Disconnect oxygen sensor connector at sensor and connect jumper wire from connector end to ground.
- An increase in engine speed should be observed (minimum of 50 RPM) for 15 seconds, then return to 1200 RPM. If engine speed does not change, disconnect 4-way "T" at temperature sensor on air cleaner, allowing engine to draw in air.
- Repeat test again, if engine speed still fails to change, replace computer. Reconnect 4-way "T". Disconnect jumper wire from ground and connect to battery voltage, engine speed should decrease (minimum of 50 RPM).
- If computer fails any of these tests, replace computer. Reconnect wires, return engine to curb idle. Stop engine and remove all test equipment.
Factory Service Tools
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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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