I have a 03 envoy with a 4.2 and something in the front on the top of my motor makes it sound like a diesel or like its got a growl to it.. It's not ticking all though there is a tick present. It gives my motor a vibration and u can see it when it's idling. It also never goes away and can hear it in the cab pretty good. I used a long screw driver to hear with and I get it on the top filler neck on the valve cover and I get it on the alternator as well. alt is new a few months ago. it has 170,000 and never had a water pump or fan clutch installed as it's never been really broke or repaired, knock on wood, mine must have been built during the week.. lol.. Any help or info?