Just a thought: Does it "use" the oil? Not leaking, and not coming out the tail pipe as blue smoke, but for some reason, the oil level is going down over time? A motor that doesn't have much life left, will go through oil, without you even knowing it. If it's your daily driver, check the oil level every couple of weeks. If it's going down, and there are no leaks, you have a serious problem.
@fortune4you, I think you did the right thing. Sounded like a wrist pin knock, which is loud on a cold start, then lessens after it warms up, but is still there, and can get louder, depending on your work load on the motor. I had a car do the same thing.
A "tick" sound usually doesn't mean major problems. But a "knock" sound, means bad news. They are two different sounds, and very easy to tell apart. The bad knock, is the one where it gets louder when you apply load to the motor. For instance, taking off from a stop light, or going up a hill. I had a car, that had this kind of knock, and it just got louder, and louder, and then it quit. Took it apart, and the camshaft broke into 3 pieces, which broke thru the valley, and landed in the oil pan, anlong with many rods and lifters. It also, spung the 5th piston right off the crank. That is an extreme example, but I learned the difference between a "low" knock and a "high" knock. Tick, tick, tick, like a clock, is high, bang, bang, bang, is a low. (deap and throaty, well, to me anyways :th_winking: )
I've talked with my gear head friends, and read here, that the "tick", "high" knock is a common thing with these 3.1's. Seems GM had these motors alittle tooooo tight, and when they get worn in, they start to loosin up and make sounds. Expectations of overhead cam motors I suppose.
I hoped I helped with all my rambling. :th_laugh-lol2:
