Check the Secondary Air System Check Valve

For cold starting a gasoline engine, a "rich" mixture is necessary, meaning a mixture with excess fuel. Since the catalyst has not yet reached its operating temperature during this condition, a significant amount of carbon monoxide and unburned hydrocarbons is formed during the time between cold starting and the lambda adjustment.

By injecting ambient air rich in oxygen into the exhaust manifold (secondary air), a post-combustion of harmful substances occurs at that point. In the secondary air system, a check valve ensures that secondary air reaches the exhaust manifold only during cold starting and prevents exhaust gases, condensation, and pressure spikes (due to misfires) from damaging the secondary air pump.

Open the hood, lift the windshield washer fluid reservoir, and locate the check valve between the secondary air pump and the exhaust manifold: then remove the hose connecting the valve to the pump, the vacuum line, and the two mounting pins of the valve to the exhaust manifold.

The valve can be tested with a manual vacuum pump in the disassembled state: - if the valve does not open when vacuum is applied, it must be replaced; - if the vacuum applied with the manual pump decreases, the valve membrane is not sealing; - any deposits on the side facing the pump indicate a leaky valve.

After performing the checks, replace the valve if necessary and reset the engine anomaly light with appropriate diagnostic equipment.