* Heat-related problems: This is a strong suspect. Holding the engine at 4000 RPM at a relatively high speed (110-120 km/h) in a lower gear puts significant strain on it, generating substantial heat. Several components could be affected:
* Overheating: The engine coolant might not be able to dissipate heat effectively at this sustained high load. This could trigger a temperature sensor to activate the warning light and potentially put the engine into a limp mode to prevent damage. A restart allows the engine to cool down.
* Sensor failure due to heat: Various sensors (e.g., oxygen sensor, mass airflow sensor) might temporarily malfunction due to excessive heat. The restart allows them to cool and possibly reset.
* Fuel delivery issues under high load: The fuel pump or injectors might struggle to deliver sufficient fuel at the high demand created by the sustained high RPMs and load. This could lead to a lean condition (not enough fuel), causing misfires, triggering the warning light, and resulting in power loss. A restart could temporarily alleviate the problem.
* Ignition system issues under high load: Similar to fuel delivery, the ignition system (coils, spark plugs) might be struggling under the stress of high RPMs and load. A weak coil, for example, might fail to provide a strong spark consistently, leading to misfires and power loss. The restart allows for a temporary reprieve.
* Variable Valve Timing (VVT) or other actuator problems: If your engine has VVT, a problem with the system or its actuator could cause issues under high load. A temporary failure could lead to poor performance and then recover upon restart.
* Loose or faulty connection: While less likely, a loose or heat-sensitive connection somewhere in the engine's electrical system could be intermittently breaking under high load and heat.
What to do:
It's crucial to have a professional mechanic diagnose the problem. Simply restarting the car and ignoring the warning light isn't a solution. The underlying problem needs to be addressed to prevent potential engine damage. The mechanic will likely use a diagnostic scanner to read the trouble codes stored in the car's computer, which will provide valuable clues about the root cause.
Don't continue to stress the engine by repeating the high-RPM, high-load scenario. This could lead to irreversible damage.
