Please, someone have an idea. In my 2000 Altima, 65% of the time I accelerate qucikly I get a strange grinding noise coming from the front passenger side of the engine. It almost sounds like a turbo blow-off valve, but I don't have a turbo. When it does happen, i usually feel a slight loss in power, and the sound never lasts more than a second or two. Once it was really bad and I experienced a great loss in power while accelerating onto the freeway. My mechanic couldn't find anything majorly wrong but this is annoying. Any help?