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Q: Failed emissions, says that bank system 1 is too lean. The car had sat for almost a year.

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The car had sat for almost a complete year and had some problems with the intake manifold but we got it fix and we took it to emissions and it failed because it said that the bank system 1 is too lean. We just got a new knock sensor. We're wondering if it has to do with the IAC valve because it had sat for so long or if there is a vacuum or tube leak going on, so do we need to clean it or just get a whole new mass air flow sensor?

My car has 260000 miles.
My car has an automatic transmission.

A: Hello there, thank you for asking about you...

Hello there, thank you for asking about your 1999 Nissan Altima. You need to fix any vacuum leak where un-metered air is getting in to the intake manifold. The additional air getting into the engine will cause the lean codes.

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