Fault Phenomenon: Foton Raysta L18 exhaust is normal when cold. At high altitude (operating temperature), engine power drops, black smoke appears, and eventually loses power.

Troubleshooting Process:
– Checked intake system: intake lines no leaks, no blockages.
– Checked turbocharger: turbo rotor turns freely, no sticking.
– Checked intercooler: intercooler cooling normal, no blockages.
– Measured intake pressure at operating temperature: found insufficient intake pressure.

Root Cause: The wastegate actuator sticks due to heat, preventing normal regulation of boost pressure.

Required Parts: Wastegate actuator.