Hello, just bought myself an 05 s2000 and when i drive it at low rpms(lower then 2000) it makes a rattling noise until I give it more power. When I gas it to around 500 rpms in neutral it rattles for about 3 seconds then goes away (I quickly give it gas and let go). Friend said it might need valve adjustment, I also heard that it could be spark plugs.
Also once in a while it drops rpms and dies at a stop light.
It's always been stock but the owner never really changed anything in it, didn't give it too much love.
New to s2000s and any info would help, thanks.

 

If you are not a troll...First, don't drive it below 2K rpm. In fact, try to keep it above 3K, or the very least 2.5K. You are lugging this engine below 3K rpm, you are really lugging it below 2.5K. Get used to a new paradigm of rpm range, where 4K on the highway is your new normal.

Second, you should be idling above 500, so if you have to rev it just to get to 500, your idle is so low its hard to believe it can stay running at all. IAC needs to be cleaned? Vacuum leak? Check these first. Fix your idle speed, don't lug the engine.

 

pull the plugs and check them. 16mm sparkplug socket, 6" extension and a ratchet. and a ....6?mm allen wrench

i prefer NGK brand, DO NOT USE AUTOLITE! use either ngk or denso.

 

Assuming the the engine is running OK, could the 'rattle' noise you are hearing be the clutch? Only notceable under part throttle?

Just a thought.