HUSQVARNA 550 XP MARK II Xp Mk Ii Autotune Running Rich

Carburetor Fuel Solenoid Valve

This solenoid is the actuator for the AutoTune system, modulating fuel flow via high-frequency pulses. If the internal plunger is stuck or the return spring is weakened, the valve stays open too long, leading to a persistent rich condition that the software cannot overcome through logic alone.

Carburetor Repair Kit

The metering diaphragm within this kit controls the fuel pressure entering the venturi; if the material has stiffened, it fails to respond accurately to the pressure differentials required by the AutoTune system, resulting in excessive fuel being drawn into the combustion chamber.

High-Flow Air Filter

A partially restricted air filter reduces the mass of air entering the cylinder. In an AutoTune system, while the computer attempts to compensate, a severely clogged filter can shift the stoichiometric ratio beyond the solenoid's adjustment window, causing the engine to run rich.