2006 Acura TL engine knocking!

OK lets put the brakes on replacing more parts until we figure out what the problem is. Replacing the valve springs was a mistake as you found out. If that was the problem you would have seen one that was broken or something. If valve springs have an issue it will show up at high rpm NOT low rpm unless one is broken. The noise does sound like it’s in the top end to me based on the frequency. I think the first thing you should have done is check the oil pressure as that would have told you if you had an oil pressure problem. If you do have an oil pressure problem then the top end of the engine will be the first to suffer and make noise. Also given that one cylinder head has been replaced it is possible that they didn’t get things lined up correctly or left out a key part that helps bring pressurized oil to the cylinder head. As an aside, what viscosity oil are you running? If you’re not running what’s on the cap then change the oil to the correct type.

The ‘extra’ valve components on the intake side are for the VTEC operation. You’ll notice that there are 3 cam lobes on the intake side. I’ll post a video to how VTEC works for you here but first I’d like to point out what might be your problem. If you are running the correct oil and you have good oil pressure the problem MIGHT be the lost motion follower for the VTEC on cylinder #5. These are there to help keep the rocker arm from flopping around when VTEC is not in use. Thus preventing a noisy valve train. You could have checked these when you had the rocker assembly off. They should have some resistance when you compress them. I don’t often see a problem with these but since so many people have been in there messing around something could have been damaged. It also doesn’t look like that engine got regular oil changes which could mean that the oil passage going to the lost motion sensor could be clogged starving it for oil. It could also be that too think an oil viscosity was used thus damaging the part due to oil starvation. Here’s the link how VTEC works. Keep us posted on your progress and stop replacing parts till you have some evidence they’re bad.

You should buy the factory car manual to know the correct oil pressure.

https://www.ericthecarguy.com/kunena/10-Repair-Central-The-How-To-Forum/43532-get-the-right-repair-manuals-for-your-car

Engine oil pressure tools on ebay. You have a plug on each car engine to plug this tools and check the presure. You need your manual to find out where and how much is the pressure.
http://www.ebay.com/sch/sis.html?_kw=Vintage+Mac+Tools+Automatic+Transmission+and+Engine+Oil+Pressure+Tester+-+400psi.

Until you gather more data we still in hypothetic cause. It’s might be an piston slap if you overfill the engine oil and run for a long time whit your car at hight RPM. The piston will expand a little bit if It’s hit the engine oil. But It’s rare and you really need to overfill It and go hight.

Thanks for the update ! banana:
So, did you change the piston or you just screw down the piston screws ?

By far the better choice then buy a new car ! B)