Nissan Repair: 2000 nissan maxima, air control valve, nissan maxima

Question
I recently replaced my factory battery with one from walmart.Ever since i did every time i start my car it revs really high at start up then idles normaly.Just recently it started to make a loud clacking noise in the engine that sounds like a diesel i can tell its coming from the side the timing chain is on.It almost sounds like the timing chain is loose. I read somewhere that the timing chain tensioner works off oil pressure.The car still runs like a top and only has 81000 miles on it. Can you tell me if any of this is related to one another or if you've heard of any of this before

Answer
David,

Sounds like the oil pressure is not getting up when the engine first revs up.  Change the oil to Mobil 1 5W30 and see if the noise goes away.  If there is sludge in the oil galleries this will clear the problem.  The new battery should not cause the high rev when starting so you need to get the car scanned to see what is going on.  Sounds like the idle air control valve is sticking or the throttle position switch is getting old and giving an improper reading.