I have a 1998 Cavalier (147,000 miles) that has made a ticking noise when I start it. However, revving the engine will quiet the noise before driving. Recently, it began making a extremely loud grinding noise when starting, that too will quiet when the engine is revved, but comes back when I accelerate. It does not lose power when I accelerate, but it feels horrible.

Unfortunately at 140,000 miles much like humans parts start to wear... now you can try to flush the oil system...I DON"T RECOMMEND IT.... I have seen engines tear apart from engine oil flushes.... drain refill the oil/filter with new oil and an additive may help, or pin down the noise to what lifter is going south and have it replaced... may end up being a very expensive repair depending on what they find when they open the engine up with high mileage...or just continue driving it untill it completely wipes out... I do belive its a hydraulic lifter that is not pumping up causing the tick and if so they usually last a long long time noisey.