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.
Cold Start Injector
Most Toyota models use a cold start injector which delivers additional fuel, and a start injector time switch which controls operation of the cold start injector. Some models use an Idle Speed Control (ISC) valve, while others use an Auxiliary Air Valve (AAV) to provide additional air during cold engine starts and warm-up.
The start injector time switch limits cold start injection to 1-12 seconds, depending upon engine coolant temperature. When engine coolant temperature rises above a specified point, bi-metallic contact breaks ground circuit of cold start injector and cold start enrichment is by-passed.
The ISC valve performs the same function as the auxiliary air valve. Mounted on the throttle body, the ISC is a solenoid-actuated valve which provides additional air during cold engine operation. It also maintains idle speed during air conditioner operation. The ISC is controlled directly by the ECU.
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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.