2001 Toyota Corolla O2 sensor

Hello

There are several ways to check for a vacuum leak. You can use a smoke machine and follow the smoke with your eyes. You can let it sit with engine off for a long time, then start it cold and immediately spray all over the vacuum hoses with carb cleaner. If spraying a spot with carb cleaner makes a change in the sound of the engine suspect that area has a leak. Carb cleaner can damage paint and rubber so be very careful with it. Vacuum leaks often make a hissing noise. Also note that with a vacuum leak fuel trims tend to go rich (positive) at idle, if you have a scan tool that reads them. Your actual sensor may not be at fault here. It may be wiring to the sensor or dirty/faulty components connected the MAF sensor circuit. It could also be a faulty component which is making the MAF sensor also go bad much quicker than it should.

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