As others have said it’s difficult to say without seeing the car. However a dirty spark plug could be due to incomplete combustion, oil in the chamber and even over fuelling. If you’re taking plugs out you may want to do a compression test - this will also tell you how healthy your engine is.
Which country are you in?
United States I can make a video of the sound when I home
Sounds like you have dropped a washer or something like that inside one of the intake manifold (tubes)
I have done it myself and if you spotted that without turning your car on then you have a chance of taking it out, but once the motor has been started it usually imbeds the metal piece into the aluminum piston and you will not be able to get it out without taking your engine apart.
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Yea I’m starting to think that’s what I did I started it about 5 times after it happened but never moved the car, when u say taking engine apart it consists of like getting inside the head of the car removing the head gasket and everything?
Also is draining the oil a good way to find out if there is any material left that caused the damage
At this stage draining oil will not show anything since small pieces have to go through everything. There shouldn’t be any on those yet…
Yes removing the head and inspecting each cylinder… When I did it I thought that washer just fell on the ground and didn’t care, but when I started it there was an annoying metal on metal sound. I didn’t drive mine either but was too late. had to take the engine apart.
If going that route you might as well do the whole rebuild process… That way the engine will run for many more miles. Especially if you have high mileage
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Well, if a washer or bolt got in the intake, it wouldn’t matter if you moved it or not, just starting the engine and letting it run would have allowed the foreign object to go into the cylinder.
One time we had a chevy 350 v-8 get an intake bolt dropped in there. Started and idled fine because the bolt was too big to go through the valve apparently. Started revving and holding high rpm and heard clickity clack and boom, engine died. Then it wouldn’t start. Got a compression gauge, found 0 compression on a cylinder. Removed the head and found the bolt halfway sucked through and was holding the valve open. That truck didn’t move either, just was running it in the bay.
Does your oil pressure gauge work? check for oil pressure, check for glitter in the oil. Someone gave good advice about listening around with a screwdriver, even just being able to tell top of engine or bottom of engine is a big plus in your situation.
Yes, draining the oil and then taking a magnet through it to see if there’s any ferrous material, you can also remove the oil filter and carefully cut it open and unravel the paper element and see what all is embedded in the pleats.
O ok did u rebuild yours by yourself? Wondering if I could it it’s a pretty easy job
No, I did not. Don’t have the space.
I just got a used motor from the importer. BTW, what year/model is it? maybe it will be cheaper to go that route… One more thing, usually if a metal object has fallen in the air intake manifold it almost always bends a valve. Just be ready for that.
1993 Mitsubishi 3000gt na model
I see a rebuild kit for 380 not sure if that’s good or not
If you have a naturally aspirated model you can drop the oil pan with the engine in the car.
We are getting ahead of ourselves diagnosis wise, but if you were desiring to rebuild the engine to get rid of a rod knock for example, you could bearing slap the bottom end. As I was saying earlier, if you started it several times after the repair and it was not clacking, then the top end of your engine should be good. Rod knock / spun bearing is common and if it were me i’d drop the oil pan, remove the lower girder and inspect the crankshaft journals and the lower rotating assembly. If it’s just wear, you can use emery cloth and put new bearings in there (probably $60 at any parts store for the good quality stuff) and put it back together. There is a video on youtube of a young kid doing it, his first time ever in an engine and he is bearing slapping a lower end. Cool video.
If you get in there and discover it melted and smeared around, well you spun a bearing and need machine work so the engine needs to come out. But you’ll know the extent of the damage and be able to fix it without pulling the engine if its not too bad.
O ok thx a lot so u recommend I drop the oil pan and inspect the lower end of the engine once it’s removed? And look for shavings in the oil ?
The last time I started it, it was still clacking and the idle kept getting higher
Also would it be recommended to buy a boroscope first and check for anything that has dropped in the manifold or cylinder
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Definitely check inside with scope first. I can’t help feeling that you are about to drop a ton of money into work that doesn’t need doing.
The problem with forums is that we can only guess what the problem is. Don’t go jumping in at the deep end. Diagnose the problem and repair it rather than strip a perfectly good engine.
It is highly unlikely that you spun a bearing at exactly the same time as changing the plugs so why start there.
Look inside the bores with a scope to see what is going on. You may need someone with an experienced eye to help you.
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I really appreciate the help definitely will try the boroscope first I trying to get to point where I can fix everything on my car, way to many shade tree mechanics in my area but if needed I’ll take it to the shop where I normally go and let them diagnose it
Yes, do exactly as Joe90 is saying… Start from the simplest and work your way up.
BTW, it’s funny that I did that to my 1993 SL… 
No, i don’t recommend pulling the oil pan to look, I’m just pointing out it’s very doable if it comes to that in the future. As i said earlier we were jumping ahead in the diagnosis but I’m happy to answer questions that you ask.
To be honest i could maybe give you some better advice if you were interested and wanted to take our time more with our questions and answers and do some checks, but I don’t have enough information to even know if the problem is top end or bottom end. I mean, Joe is very correct that it’s much more likely something went wrong during your work but only you know what happened, you know? I mean, in my mind, do you have any leftover bolts or nuts? Were there a lot of washers you were messing with and could have lost one in there? I mean that’s unlikely too, but something happened.
It’s very unlikely the oil pump failed, i’ve never seen this style fail unlike older chevy v8 style, i have heard of these getting the oil pressure relief valves clogged with trash and that lowers overall pressure and can wipe an engine. But the odds of this being you problem now are so small. All I was trying to say earlier is, If you had looked at your oil pressure gauge like I would have while it’s knocking, and if you were used what it looked like normally, you’d have double the confidence in moving forward with your diagnosis. I wasn’t asking you to check the oil pressure because i think the engine is shot and needs to be rebuilt, but rather i’m hoping it’s ok and normal and we can quickly move past those concerns without doing checks and taking time. You gotta remember, in my mind i’m still thinking this could all be lifter tick and not a rod knock. I have no idea your experience level or even if you’ve ever heard this car run before, you know?
I mean, if you think something is in there and you’ve been running it already, just remove the upper intake and the spark plugs and bar the engine over to TDC on each cylinder and fish a telescoping magnet in there. I have a flexible one where the magnet is not exposed until you push a button on the end. So i can fish it down in places without it sticking to all the walls and when i get where i want i push the button and the magnet pops out. If you dropped hardware in there i’d imagine it’s ferrous and will stick to a magnet. Borescope would be handy too.
Let me know if i can help. Good luck.