try to change your driving style, the ECU gets confused when you coast to lights in neutral. It want to shut down fuel but it needs to maintain an Idle. My car did this same thing and it was always off a stop. I started coasting to lights in gear and would clutch in at about 1500rpms and the problem is pretty much gone. It only does it slightly when the A/c is on and thats normal since the engine is under more load. The s2000 is a ruff car to drive, it deff has its kinks but i love it. this car is amazing !!

 

I've noticed this since I got my car about a year ago. Anytime I'm using AC or any other systems that caused heavy electrical load it seems to be more pronounced. My friend's AP1 does the same thing. Not too worried about it.

 

Would a more powerful alternator solve this? I had one in an old civic and it did wonders for the car... I got mine from ohio generator I think

 

Mine does the same sometimes. Seems it's a "normal" bug. If I rev it a little from idle it does the same, the RPM drops sometimes at 600 RPM and after a second comes back to 900-1000.

 

i think it might be normal because that happens to me too ^

 

I agree with ljsimp, watch the rpm drop to 1k and then push in the clutch. That worked for me, I read the same thread hes talking about, pretty much said dont coast in neutral, always try to rev match (if possible) and have it in gear. Might also want to replace IACV, theyre only a few bucks at Advance, Autozone, etc... Its worth replacing it if youre having these kind of problems.

 

i wonder how this would work out, sounds interesting

 

I don't think it comes from the electrical part so I doubt that an alternator changes enything.

And the IACV can be cleaned with brake cleaner spray, why replacing it?
I did that myslef on another car and I don't expect this operation to be more complicated on an S2000.

 

Its not the idle thats the problem, its the fact that the ac compressor relies completely on the motor which lowers the idle.

The only solutions that i could come up with that MAY solve the problem would be:
1. Bigger alternator, would solve alot of the issue regarding dips in idle when using electrical components (window motors, top, etc), and although the compressor isnt, all the fans and motors are.
2. Manually raising the idle. Problem is worse gas mileage, wears clutch faster, inefficient, etc.

IACV cleaning, spark plugs, air filter, tb cleaning, map whack, ecu reset, nothing fixes the issue... I've already done all of that.

Ohio Generator's Website I strongly think this would really help if not completely solve the issue. Once mine goes I may look into this for an upgrade.

 

In the heat our engine will bog or shutter even with the A/C off, of course it will make it worse with the A/C on since the compressor is on. You can always try the different alternator man. If your willing to spend some money on a bigger alternator to experiment with, cool. If you do, be sure to let us know how it goes. In my opinion, I highly doubt it will solve this problem. Yet, you could show me wrong if it works.