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			Originally posted by tcodi 
do valves start to make noise when they get out of adjustment.  I'm asking about by grand cherokee v-8 with 150,000 miles on it.  For some reason when I step hard on the gas, even if its on the highway and the rpm's stay constant, I hear the rapid tapping of something.
It has nothing to do with rpm, just throttle level.  I don't know what this is.
Could the valves be out of adjustment from the age? 
			
		
	
  sounds like spark knock to me, try a better grade of gas and see if it stops. :cool: