2016 rdx
Bought cpo at 30k
currently 80k

Just two months ago. The rdx has been making this sound. I’m not too sure what it is.

at first maybe it was the oil filter / oil. It fixed it for about 1 week and now it’s worse. Been reading through the forums, however did not find anyone with this problem.

https://youtube.com/shorts/chZq18a3Um4?feature=share

 

First you need to determine where the sound comes from, it can be top, bottom and timing mechanism. The sound is very much like a rocker arms, so if you determine that the sound is coming from the top, well, you need to remove the valve covers and visually inspect whether all the VTEK springs are in place. The noise is very similar

 

It’s coming from the top end. The noise does go away after 5 mins or so. Will that still suggest rocker arms?

 

I don’t know, it needs to be disassembled and diagnosed.

 

+1 on this. There's no way to tell unless you can visibly see it all.

 

The advantage of our engines is that there is no chain and if you can’t find anything visually, then you can put on the intake manifold without valve covers and start it for a short time to find out the exact place of the knock.

 

I am not all that familiar with my RDX other than doing general maintenance at the moment since it is low mileage and a daily driver.

But how does the VCM work? Does it open valves in dead cylinders and cut the fuel to the injector. Might the noise come from the valve mechanism? Is there a solenoid that activates the system and it is not working as intended. Just a guess.

 

The VCM just keeps all the valves closed, therefore, for some people on worn engines, oil is sucked into the cylinder during deactivation. I wonder how, in your opinion, the fuel can be cut to the injectors?

 

Well the VCM technology is a first for me.

As for the injectors, do we still want them to spray even when the cylinder is not firing? If I can cut individual injectors on my scanner, the ECM can also if a mode such as VCM is enabled.

In any case, it would be nice to see a full explanation from Honda on this system.

 

It's elemenary, the valves are closed, ECU does not send a signal to the ignition coils and injectors, the vibration due to non-working cylinders is damped with the help of the engine's electromagnetic mounts.

 

I've been trying to figure out mine as well (2016 RDX), somewhat similar. Only happens in cold weather when cold starting. I was advised that it might be the valves that need adjustment, which I will do at the 100k mile service (currently at around 93k).
Here are some clips:

 

Come to think of it, last winter I also heard a sound just like in that video after getting out of the car while I was stopped at the community mailbox. The engine was warm at the time. A "ticking" sound but a bit louder. Sounded like a solenoid valve oscillating. That was the only time I ever heard it.

Can't be a valve unless it does it all the time since they are a threaded adjuster and lock-nut type and not a hydraulic lifter.

 

So what are the pressures within the cylinder as the engine is turning over with properly closed (air-tight) valves? Do the valves close at the bottom of the stroke, the top of the stroke or mid-way?


As expected.

 

The valves are fully closed, which means completely closed.