Strange knocking sound
 

Hi I have a weird knocking sort of sound coming from the engine, it mainly seems to do it when the car has warmed up a bit, the only way I can describe it is like when the car does that judder sound if the revs drop too low but it's fairly consistent at idle but doesn't always seem to sound the same. It's doesn't seem to be a constant knock knock knock etc, it can make the noise a couple of times and then stop for a sec and then it could do it a few more times etc and just carries on like that, not really a proper pattern to it, it's weird sounding. I don't think its loud enough to be picked up on a video but I can hear it all the time, it's been doing it for a while now but seems to have gotten a little worse. When I rev the car or give it the beans I can't hear it and it seems to be performing normally, just a little worried it's something bad now. :(
Any help or advice is greatly appreciated.

Err how about don't drive it until you find out whether the knocking is something to worry about?

Had the rocker cover off? Checked the cam tower bolts? Inspected anything? Dropped the oil and checked for metallic flakes in it? A healthy engine does not knock.

Yeah I probably shouldn't drive it and I've been limiting how much I use it.
I had the rocker cover off a couple of months ago to do the valve adjustment and everything looked ok as far as I could tell, some of the valves were well out. I did an oil change at the same time and inspected the oil and it looked clean to me, couldn't find any bits in it.

Quick and easy one to determine bottom end failure, wizz off the VTEC solenoid, 3 10mm bolts and it's off. It has a high pressure oil feed from the bottom end and it's where a lot of bearing/foreign material ends up in the filter gauze. You'll soon be able to tell if it's shagged!

Only other thing worth mentioning, depending on the year of the S, if it's a late model 07 onwards, you may be exhibiting signs of crank walk/excessive end float, which presents itself more when warmed up. Only way to diagnose this is with a DTI gauge

I’d be looking back at the last time the engine was touched in case something has come slack, is it a hard knock bottom end noise or a lighter tappety rattle, that might be a clue as to where to start.

Hi thanks for the replies, I actually replaced the VTEC solenoid gasket when I did the oil a couple of months ago and it was completely clean, it's a 2002 car.
The noise is quite quiet so I have to have the music off to hear it usually, sometimes I can't figure out if it's a knocking sound or a misfire/idle problem and it's causing the sound, it's very odd and I can't figure it out, last time I opened the bonnet to listen, I couldn't really hear anything, it's only when I'm in the car, the idle does drop quite regularly but doesn't stall.

What condition is the belt / tensioner pulley bearing in? You can listen to knocking by using a screwdriver, metal tip on what you want to listen to, plastic handle touching your ear.

Clearly this is not meant for battery terminals - just saying :)

Brand new belt and bearing was also fitted a couple of months ago haha.
I changed...
Oil
Oil filter
VTEC solenoid gasket
Belt
Bearing (was a little wobbly and sounded rough)
Rocker cover gasket
Did a valve adjustment
Had the battery tested

Maybe I should try the screwdriver test haha, I've tried that on injectors in the past

post a vid, might help

i'd say in my limited experience a bad knock follows revs but dont take chances, these are £££ to rebuild

I'll try a video soon and see what it's like, thanks for all the help