Question

I got the engine code Insufficient coolant temperature fuel loop on my Toyota, what does it mean?

Answer 1

Insufficient coolant temperature for closed loop operation, When the engine is first started the operating temperature is cold, for complete combustion you need more fuel than air ratio. The engine feedback per sensor are ignored. The ECM monitor the engine operating temperature and gives fuel per temperature situation and adjust timing accordingly. When the engine reaches operating temperature, Combustion is much easier so less fuel is needed and more air to fuel ratio is needed, maintaining this temperature operation is optimal for fuel economy,  This is now closed loop At closed loop the engine sensor are now used . ,To maintain a optimal engine temperature a thermostat is used, If the thermostat is open for too long or is missing, fuel economy suffers