I recently purchased a 2004 5.3 liter Suburban. It runs and drives perfect, but at idle it has what seems to be, a harmonic vibration. It vibrates in neutral or in gear, with the a/c unit on or off, it is not a bad vibration but it is annoying to me, most people probably wouldnt notice it. The vehicle has 60000 miles on it. The dealer acted as though nothing was wrong with it. You can increase the RPM by only the slightest amount and the vibration stops immediatly. The check engine light has not come on. I was wondering if anyone else has experienced this problem, or could tell me what may be causing it. I have already tried putting fuel injector cleaner inthe tank and cleaning the throttle body but this did not help. Any suggestions or comments would be greatly appreciated. Thanks.