2007 Honda Civic Coupe EX
Every time I gain speed, there is a louder than usual noise coming from the either the middle of the car or the engine. The loud sputtering sound always starts exactly at 4000rpm and up. The best way to really describe the sound is that is sounds like a fast/loud misfires while driving or metal grinding. I’ve tried looking for leaks by covering my exhaust with a rag and nothing. No exhaust smell either through the vents. My mechanic plugged it into his computer and no codes. Please help!