I have observed an irregular rattle that seems to be coming from from underneath the valve cover. This was heard only after the engine was let to isle after a short drive. At the time when it happened, I noticed that the sound goes away if the ac is turned off (I turn off the ac at 02:55). I don't think it has anything to do with the ac system itself it feels for like it goes away if the engine is relieved of the ac compressor's load. If you have had a similar experience, please share how you went about getting it fixed.

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