When i turn my ap1 on. Rpms jump to 3000 and then just goes down super low like 400 rpms.

 

I'm pretty new to the S2000 but I'll try to help. Is it cold or does it happen only on a cold start or every start? It may be your IAC valve sticking a little bit when you start it up?

 

Do an idle learn procedure. Simple first step before touching anything.

 

what is an "idle learn" procedure/ ive never even heard of this

 

You basically get the car warm, then disconnect the battery or pull the ecu reset fuse for about 30 seconds. Reconnect the battery or reinstall the fuse. Make sure all electrical accessories are off (no heater fan, no radio, no lights, etc.) , if you have drl's engage the e-brake. Start the engine and don't touch the accelerator, let it idle until the cooling fans engage a couple of times, then shut off the engine. That should be it. Hopefully the ecu learns what idle speed is needed and controls the IAC properly from that point onwards.

 

It was that. I cleaned out the iac the day before.

 

That sort of info can be very helpful in the initial post...

 

i should do this. never did it after the intake install. idle kinda "hangs" from time to time

 

This is my 16 year old son't S2000. Car was shuddering/stalling at idle. These forums told me to clean the IAC. Did that and improved but still not great. Then did the relearn procedure. 3000 rpm to warm it up and then 5-6 minutes idling. Car is now running perfect.

1 note - I wasn't sure if the fan had come on (meaning the car was at operating temperature) and took my foot off the gas to listen and it was still running rough. Got my daughter out to look at the fan and once it came on I took my foot off the gas (figuring it would stall like it would've just a couple minutes earlier). Nope. Held 700-800 rpm perfectly with no foot on gas. Amazing how quickly the problem was solved. Car is running great now. Also replaced the clutch master cylinder (leak) and slave all by just following these forums and DIYGuys videos on Youtube. Really driving great.

Thank you all.