Engine ticking noise when accelerating

If it is indeed piston slap, there are a couple of options that you could explore. One is replacing the engine. The second involved a lot of tear-down and machine work. However, I would only consider these options if you absolutely cannot live with the noise. Have a reputable mechanic check the car out - including a compression test - if he believes that the car is mechanically reliable, and you can live with the noise, try not to worry about it. There are many 3.1L engines that have been experiencing the same issue.

If it is indeed piston slap, the lifters will not affect the noise. Piston slap will cause premature engine wear - specifically on both the cylinder bores and the pistons. This will eventually lead to oil consumption. With excessive piston ring to cylinder bore clearance, engine oil will enter the combustion chamber and be burned. Engine longetivity will be adversely affected.

My neighbor owns a 1998 Buick Century with a very similar noise. Her's is not very loud and quiets down considerably when the engine reaches operating temperature. I've maintained the car for her for the past several years. It consumes less than a quart of oil every 3000 miles. She's learned to live with the noise and the car has over 100,000 miles. I wish I could give you a guarantee that your car won't suffer adverse effects from the noise, but I can't. All I can say is that this noise is a very common characteristic of this engine. Keep it maintained and listen for changes. If it gets worse, further investigation may be required.

Keep driving it. If it's been happening for a year without adverse affects, I'd like to believe that it's just the piston slap noise that affects a great many of these engines. And like I said, keep an ear open to see if the noise changes or gets worse. Also be sure to check your oil regularly and pay attention to excessive oil consumption. Good luck - I hope you get many more miles of good service from the vehicle.