Knocking sound under acceleration

[h6subie]

Hi guys, it's good to see the forum back up. I have a completely stock 2007 Liberty tbSTI with 140,000km and it's been making a knocking sound for at least the past 2 months/2000kms and it hasn't gotten any better or worse during that time. During light acceleration through gears 1-2-3 it makes a light knocking sound at around 3000 rpm or so. As soon as I let off the throttle or if I were to step on it a bit more, it'll stop. It only does it when warm and only when accelerating in gear. It might make a tiny bit of knock if I rev it just right and really slowly around 2500-3000rpm in neutral but it doesn't really do it as much. It doesn't feel like there's any loss of power and sounds fine under heavy acceleration.

I took it to a Subaru specialist over a month ago and they said I'll need a new engine but they wouldn't say what was wrong exactly. But then again a few weeks before that, I had them look at a knocking sound when idling and they said that was fatal but it turned out to just be a loose spark plug so I'm not sure if I should trust their diagnosis. I'm hoping it's not a spun bearing but I am preparing myself for it. I've uploaded a crappy video below which hopefully captures the sound. Any ideas?

https://www.youtube.com/watch?v=NxYGTcL8svg

[SuperS0nic]

Definitely pull the timing cover off and check the tensioners. If there's play in the belt I wouldn't drive it, I'd get a fresh OEM belt kit fitted asap. Check all your plugs too. If it was a rod bearing, it'll stumble slightly and make a very noticeable rattle on start up and it gets bad quick. When my rod bearing went it was a 10 minute drive pretty much from first rattle to being blatantly obvious and I was nana driving it home.

[RX25SE]

Have you checked the oil pressure when hot?

If you can replicate the sound by giving the engine a gentle throttle blip in neutral, try isolating each cylinder one at a time by unplugging each injector. The unplugged cylinder that produces a quieter/no knock may have a spun bearing.