Fuel Injector Service

 

Fuel Injector Service

As a vehicle approaches higher mileage, you can generally expect intake valve deposits (IVDs) and injector deposits. Their onset can vary widely depending on driving conditions. Engine operating temperature, intake manifold speed (RPM) and hot soak cycles are some of the critical operating parameters affecting these deposits. To lubricate an intake valve, tiny amounts of oil have to run down the valve stem. Over time, this oil is deposited and heated on the intake side of the valve, forming a carbon cone. This has multiple effects on the intake event. The carbon changes the aerodynamics of the intake event - namely causing higher gas speed and a change in the direction of intake swirl, which affects the combustion process. The IVDs also act like a sponge, creating a delay in fuel control. This delay not only creates a temporary enleanment on acceleration but also causes a temporary enrichment on deceleration. When the throttle is closed, the intake manifold vacuum goes high, pulling the fuel out of the carbon sponge. This affects fuel control, potentially affecting catalytic converter diagnostics under OBDII. Because of IVDs and the effect of phosphorus (from oil ash) on converters, "normal" oil consumption will have to be drastically reduced to achieve ULEV (Ultra Low Emission Vehicle)  and SULEV (Super Low Emissions Vehicle) levels.

 

 

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