I have a bit of a dilemma. I just noticed a weird knocking noise and not sure its the stupid noise producing solenoid that i disconnected or its the flipping engine piston rods.
It comes from the solenoid side but unsure… any ideas?
Edit, oil levels ok (above the second hole on the dip stick)
Noise filmed from the inside
Noise filmed from the outside
remove serpentine belt and restart engine , if the noise is no longer present then its the belt and pully’s that need replacing …not a big job
good luck 
Couldn’t do that i was not home.
Right… Drove it hone 60+ miles - engine hasn’t blown up (just yet). I think its the inside the cabin silly solenoid that i disconnected and never paid attention to.
The reason i don’t think its the engine big end is because it doesn’t really sound like hammering and it goes away when engine rpm increase.
As for engine swaps… if this sucker blows its gunna get an LS or honda k series…
Does the noise change when you depress the clutch pedal?
Sounds more like a clattering clutch release bearing than a knocking engine.
will check that tomorrow but what’s definite is that it goes away when engine rpm increase.
I will pass by dynotorque and pick Craig’s brains and discuss what lump may / potentially / eventually fit in that chassis
As others have said.
Disconnect the auxiliary belt etc.
Again could be clutch related.
Could also be the cam chain tensioner perhaps?
(You have a series of guides and the actual tensioner itself).
As when idling it will slap about a bit. When the revs increase the chain tensions slightly more and the noise goes away,(well within reason).
Just another avenue to explore and may not be that at all.
Good luck.
Interesting post, my 2.0 2006 does this at times, normally after a run out i notice it when i return home and it idles ?
Have you tried the ‘large screwdriver’ method to localise the noise? Take a large screwdriver, put the handle end on your ear, and the other end on metal parts around the engine.
Be careful not to dangle hair, ties, scarves, loose clothing in there, obviously.
It definitely works - I used it many times in my youth keeping old bangers going.
This youtube video (warning: shouty American person) shows you how:
Not saying it’s your problem, my last NC had more like a squeak on idle. Sounded fine if I revved the engine slightly.
It seemed to be coming from the tensioner pulley, that’s the one bottom left near the alternator.
Looking back I suppose I could have squirted a little lube around it, or more like on the spring in the tensioner to see if that sorted it. Anyways I replaced all pulleys + tensioner and fitted a new belt. No more squeak. Don’t think the others needed replacing but for a little under £100 (DIY) for parts and another job ticked off that could later need doing anyway.
Some have had worse noises that turned out to be a pulley or tensioner causing a right racket.
Mine sounded like a diesel and diagnosed as terminal by Mx5 expert , but sorted myself by changing belt and pulleys 
Incidentally i saw a bloke on facey that his engine has rod end damage. You can hear how that sounds like (really bad tbh)
However my issue is now solved. It was actually the solenoid. After disconnecting the ducting it free up some area and i could screw the solenoid directly on the chassis. When it switches on because of the vibration it excites the chassis and the noise is amplified and this is what i could hear. A rubber grommet between the chassis and the thing will solve my issue.
Thanks all for your suggestions.
It’s nice when you get a cheap fix.
So no LS swap 
Not at the moment 
Today I have been at Craigs and he said the 2.5L duratec conversion is the easiest could be done for roughly 2k all in (with different cams but no ITB’s) and that would give me around 200 bhp and buckets of torque keeping all the car auxiliaries as is (air-condition etc etc).
He is currently doing his rx8 with a turbo’ed honda k series (and that looks a beast)
Once he’s done his rx8 he would know the ins and outs of a K series conversion (Craigs a genius mechanic btw and very nice bloke but he loves a challenge) If my engine blows I don’t know atm what I’d do.
I really want to stay NA and the 2.5L duratec is probably the easiest way forward but… the seed has been planted… so who knows…