Hi, I bought a used 2010 Acura RL listed as 'in non-running condition', the odometer is reading 233,000 km, external body in great shape. I put some oil and fuel in it, charged up the battery using external charger. After putting the battery back in, it started right up, and there are no lights on instrument cluster and no codes on obd2 scanner. I put the car in drive and it moves. On idle the car makes the regular old engine sound like there is little valve lifter tick noise, power steering pump is leaking. But when I increase the rpm to around ~2K engine makes a rattling/clanking noise (see the attached video), when the rpm go back to idle that noise is gone.

After doing some online research, I removed the serpentine belt, the noise was still there. I checked the heat shields, non of them had enough play to make noise, still I tightened them and the noise it still there. I took out the timing belt tensioner, it was still good and replaced it with newer one as I had already bought the part. Also timing belt didn't look old.

I need help to diagnose this issue, any feedback will be appreciated.

 

The sound is very low frequency, very reminiscent of a piston rod. I would first take the pan off and look at the condition of the connecting rod bearings.

 

I can try that. Is there any other method to pin point this before I try to take the exhaust out, I heard those bolts are hard to take off.

 

Always the only correct method is disassembly and troubleshooting. In your case, you can buy a statoscope, drive up ramps, crawl under a car, and have someone else repeat that knock . Once you are sure the knock is coming from the short block and not the heads, you still have to remove the oil pan and check the crankshaft, if the crankshaft is finished then you need a new engine.