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.
THERMACTOR System: Operation: Notes
The air pump supplies air under pressure to exhaust port near exhaust valve by either an external air manifold or through an internal drilled passage in cylinder head or exhaust manifold. This pressurized air, combined with hot exhaust gases, creates a secondary combustion stage which produces carbon monoxide and water.
In the MTA system, air can be by-passed to the atmosphere by a thermactor air by-pass valve and/or directed near exhaust manifold, or underbody catalytic converter. Some models may use a combined air by-pass/air control valve.
In the Thermactor II system, natural pulses present in the exhaust system are used to pull air into exhaust manifold through a Pulse Air Valve (PAV). The pulse air valve is connected to exhaust manifold by a tube, and to air cleaner by a hose.
In the Extended Idle Air By-Pass system, a normally closed Idle Tracking Switch (ITS) opens when throttle returns to idle. The ITS signals EEC module to activate by-pass solenoid valve which causes thermactor secondary air to be released into atmosphere.
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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.