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<h2>What is a secondary air injection check valve?</h2>The role of a secondary air injection check valve is to prevent the reverse flow of exhaust gases into the Secondary Air Injection (SAI) system, particularly during specific engine conditions like cold starts.When a vehicle's engine is cold, the secondary air injection check valve produces higher emissions. The SAI system is designed to reduce these emissions by introducing fresh air into the exhaust system during cold starts. The Secondary Air Injection Check Valve is like a one-way door in this system. It ensures that only fresh air, provided by the SAI pump, is allowed into the exhaust manifold. This fresh air helps burn any unburned hydrocarbons in the exhaust, lowering emissions. The check valve's critical job is to prevent exhaust gases from flowing backward into the SAI system. This would disrupt the emission-reducing process and potentially lead to higher pollution levels.<h2>How do I know if my&nbsp;secondary air injection check valve&nbsp;is bad?</h2>Some common signs that can indicate a bad SAI check valve:<ul><li>Check engine light: Illumination of the check engine light on the dashboard, often accompanied by specific error codes related to the SAI system.</li><li>Increased emissions: Higher emissions levels, potentially leading to failed emissions tests.</li><li>Poor cold start performance: Rough or problematic cold starts, including rough idling and hesitation.</li><li>Reduced fuel efficiency: Decreased gas mileage, resulting in fewer miles per gallon.</li><li>Unusual engine noises: Odd sounds like hissing or rattling may emanate from the SAI system.</li><li>The smell of unburned fuel: The presence of the smell of unburned fuel in the exhaust, is noticeable from the tailpipe.</li><li>Loss of engine power: Possible reduction in engine power, especially during acceleration.</li></ul>

Secondary Air Injection Check Valve

Air Cleaner

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Air Filter Box

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Air Flow Sensor

Air Intake Duct

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Air Intake Hose

Air Intake Manifold Actuator Control Solenoid

Air Intake Manifold Flap Adjuster

Air Intake Manifold Runner Control Sensor

Air Intake Resonator

Electric Vacuum Pump

Engine Air Duct Assembly

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Engine Air Filter

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Intake Manifold

Intake Manifold Flap Actuator

Intake Manifold Repair Bracket

Intake Manifold Runner Control Valve

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Intercooler

Intercooler Hose

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Oxygen Sensor

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Pressure Sensor

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Supercharger Pulley Drive Unit

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Supercharger Snout Rebuild Kit

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Throttle Body

Throttle Cable

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Throttle Position Sensor

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Turbocharger

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Turbocharger Gasket Kit

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Turbocharger Oil Line

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Vacuum Pump

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Air Filters & Intake Systems

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Camshaft Adjuster

Camshaft Adjuster Cover

Camshaft Kit

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Camshaft Timing Gear

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Camshafts

Chain Tensioner Adjuster

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Cylinder Head

Cylinder Head Assembly

Eccentric Shaft Actuator

Engine Timing Belt

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Engine Valve Cover

Engine Valve Cover Gasket

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Harmonic Balancer

Rocker Arm

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Rocker Arm Shaft Lifter Assembly

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Timing Belt Kit

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Timing Chain Gear

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Timing Chain Kit

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Timing Cover

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Timing-Control Valve Solenoid

Valve Cover Gasket

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Valve Lifter Guides

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Valve Lifters Tappet

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Cams, Timing & Valvetrain

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Belt Tensioner

Coolant Level Sensor

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Crank Installer Tool

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Crankcase Breather Hose

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Crankcase Breather Valve

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Crankshaft Position Sensor

Crankshaft Pulley

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Engine Oil Dipstick

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Engine Oil Dipstick Tube

Engine Oil Filter

Engine Oil Pan Gasket

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Flywheel

Harmonic Balancer Crankshaft Hub

Knock Sensor

Oil Baffle

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Oil Cooler

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Oil Cooler Line

Oil Drip Pan

Oil Filler Cap

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Oil Filter

Oil Filter Base

Oil Filter Cover

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Oil Filter Housing

Oil Filter Housing Cover

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Oil Level Sensor

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Oil Pan

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Oil Pump

Oil Pump Drive Gear Shaft

Oil Pump Pickup Tube

Oil Separator

Serpentine Belt

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Cranks, Pistons, Oil & Components

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Camshaft Position Sensor

Camshaft Position Sensor & Magnet Kit

Connector Plug

Distributor Cap

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Electronic Ignition System

Engine Valve Covers & Ignition Coils Kits

Glow Plug

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Glow Plug Relay Module

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Ignition Coil

Ignition Coils & Spark Plugs & Wires Kits

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Ignition Coils & Spark Plugs Kits

Ignition Coils & Wires Kits

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Ignition Distributor

Ignition Lock Cylinder

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Ignition Starter Switch

Ignition Switch Actuator

Kill Switch

Knock Detonation Sensor

Relay

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Spark Plug

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Spark Plug Wire

Electronic Control Modules, Ignition & Distributors

Engine Wiring Harness

Intake Manifold Repair Kit

Pulley

Engine Components & Accessories

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Active Grille Shutter Actuator

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Auxiliary Water Pump

Drive Motor Inverter Cooler

Electric Engine Water Pump

Engine Coolant Air Bleeder Valve

Engine Coolant Pipe

Engine Coolant Shut Off Valve

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Expansion Tank

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Expansion Tank Mounting Plate

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Fan Pulley Bracket

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Fuel Cooler

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Overflow Hose Connector

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Radiator

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Radiator Control Fan Module

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Radiator Core Support Skid Bar Plate

Radiator Fan Cooling Motor

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Radiator Hose

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Engine Cooling

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The engine comprises many essential elements such as the lower cylinder block, upper cylinder head(s), and the cooling & lubricating systems. With A-Premium aftermarket engine components, you can expect that your engine deliver years of reliable performance. We offer a diverse selection of engine components from air filters and ignition coils (kits) to fuel pumps to cater to your needs.

Audi S4 Secondary Air Injection Check Valve