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.
Electronic Control Unit
The Electronic Control Unit (ECU) is the central component of the control loop. See Fig 1. It constantly monitors exhaust gas oxygen sensor, throttle angle vacuum switch and coolant temperature vacuum switch.
The determined response is sent out to the vacuum solenoid/regulator, which supplies vacuum signal to the fuel metering rod in carburetor to obtain the proper air/fuel ratio required for optimum operation of the catalytic converter.
The ECU also contains circuitry that, based on engine RPM, varies the length of time required for a change in the air/fuel ratio. The ECU sends this constantly cycling voltage to the vacuum/solenoid regulator.
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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.