My service engine light came on a while ago & my car was making a pinging/rattling noise. When I got it check out at advanced auto parts they told me my knock sensor is bad. I bought a new one & replaced it & it stopped making noise for about a day. Got in my car & started driving it & the noise started again... This is beyond aggravating

 

Have you checked for codes again?

Have you tested the KS harness?

 

Your car should never ping/knock, even with a failed knock sensor because the engine computer, knowing the failed ks, dials back timing and therefore power. My car had a failed ks for like a year. No pinging and pretty good mileage too, like 23-24.

Maybe you have a lot of carbon on your internals. Try tcw3. There's a thread in here about it.