Okay so after a while of not starting a 4.0 V6, that I’m looking to pass down to my sister once she gets her license, when I start it up every now and then it sound like a knock? Or a dry chain? Lol there’s oil in the truck but it doesn’t sound good but the noise gradually goes away. And drives normal. Does have p0420 codes and plan on changing the cats soon after a year or two of avoiding it. Also can a knock sensor cause this? I thought the knock sensor code would be coming bc of the bad cats. Can anyone relate to this?