An annual production in 2001 to 1.8T, mileage of 280,000 km, the owner reflects the engine work when the sound is great. After the car, start the engine, idling engine sound is really big, but it sounds like the sound of the sound, but like the exhaust pipe leak. Asked the owner that the car recently because of the three-way catalyst plug, in the other repair shop to replace the new three-way catalytic converter.
    According to the situation reflected by the owner, maintenance personnel suspect that maintenance personnel are not in the replacement of three-way catalytic converter when the exhaust pipe bolt tightening or exhaust pipe gasket damage and leakage. Lift the vehicle with a lift, carefully check the exhaust pipe of the connection is the phenomenon of leakage, check no abnormalities. For the sake of reliability, remove the exhaust pipe carefully check the exhaust pipe pad, did not find traces of leakage. As the car is equipped with turbocharger, maintenance personnel will check the focus shifted to the turbocharger, but after the demolition of the supercharger still did not find the phenomenon of leakage, and finally the exhaust manifold is also removed to check, Or did not find the point of failure. Will remove the accessories all loaded back, start the engine, carefully listening to confirm the sound is indeed exhaust sound. But the exhaust system did not find leak ah? Is it the exhaust gas recirculation and the secondary air system leaks? The exhaust gas recirculation system introduces a portion of the exhaust gas in the exhaust system into the engine combustion chamber under specific operating conditions. The secondary air system is a process in which fresh air is introduced into the exhaust system so that the exhaust gas that is not completely burned is again Burning, these two systems are connected with the exhaust system, the two systems will be a problem?
    Start the engine again, the hand extended to the EGR valve below, you can feel a hot air discharge. Remove the EGR valve and the secondary air valve, found in the two valves on the base of a loophole, it seems the cause of the failure lies in this. Replace the base, start the engine no longer have the sound of leakage. Maintenance personnel believe that the ternary catalyst has been blocked, which makes the exhaust system pressure increases, resulting in EGR valve and the second air valve base was washed, which is the reason for the loopholes on the base.