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.
High Altitude Compensation System: Description
The high altitude compensating system consists of the Electronic Control Module (ECM), an altitude switch, and a solenoid valve. The altitude switch senses altitude from atmospheric pressure and activates solenoid valve and ECM at high altitude.
The solenoid valve opens an leans air/fuel mixture by introducing air into the carburetor through the altitude compensating ports. The ECM changes the open duty cycle and also leans the air/fuel ratio. The lean mixture reduces HC and CO emissions at high altitudes. At low altitude the altitude compensating system does not operate.
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.