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.
Jet Air System: Description
Jet Air System uses an additional valve in top of each combustion chamber to inject a high velocity stream of air at small throttle openings. On intake stroke, air rushing out of jet valve opening scavenges gases from around spark plug and produces a strong swirl in combustion chamber. This promotes high combustion efficiency and results in lower exhaust emissions.
The jet valve is operated by an extension on the intake valve rocker arm. The valve assembly consists of a jet valve, jet body and spring. The assembly is screwed into the jet piece, which is press-fitted in the cylinder head with the jet opening toward spark plug.
Cordia and Tredia models are equipped with a jet air control valve and a thermo valve to help reduce CO and HC emissions during engine warm-up operation. The control valve is opened by carburetor vacuum during engine warm-up operation to prevent too rich an air/fuel mixture, depending upon preset value of thermo valve (part of EGR system).
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.