Vacuum test
Connect the vacuum gauge to the intake manifold, start the engine, gradually increase the idle speed to 2500r/min, and observe the change of the vacuum gauge. If the vacuum degree drops at this time, keep the engine speed unchanged at 2500r/min, and then the vacuum If the temperature reading drops significantly, the catalytic converter is clogged.
Because the blocking of the catalytic converter is a gradual process in the vacuum test, and this test is a steady state process (2500r/min), the vacuum reading will not produce a significant drop. If a comparative inspection is performed in the laboratory before and after the catalytic converter is blocked, after the catalytic converter is blocked, the vacuum degree of the intake manifold will drop significantly. caused by blockage. When the fuel supply to the engine is reduced, the vacuum level of the intake manifold also decreases. Therefore, compared with the vacuum test, the exhaust back pressure test can more truly reflect the situation of the catalytic converter.
The above methods can only check the mechanical failure of the catalytic converter. The performance of the catalytic converter, that is, the level of its conversion efficiency, needs to be judged by the following inspections.