I'll guess the O2 sensor is the one to blame for running rich.
Then MAF sensor..
Besides both cat and O2 are easy to test & rule out of the equation; so I really do hope it is a just an O2 sensor for you mate (cheapest to fix!)

 

Cheers chaps, I'm gonna start with the MAF sensor & O2 sensor. Still learning the S's quirks but have observed the MAF sensor being mentioned a few times whilst browsing the forum, I'll search how to clean it (or whatever the procedure is) and begin there.

PS no misfire and drives great. Just honks to high heaven, even have to have the windows down in traffic to circulate some fresh air.

 

Technically it's a MAP sensor on the S2000 but does the same job as a MAF

I'd like to think the O2 sensor would throw a code if it had an issue, but the MAP can be faulty and not throw a code. Check the connection to it and maybe see what pressure readings it's giving (engine off, and at idle) if Revs will log that.

Of course this might all be a red herring, I'm wondering if there's something wrong with the fuel tank / EVAP charcoal canister - you shouldn't be getting strong fuel smells in the cabin. The fuel tank is pressurised so if there's a leak it might vent into the cabin. Just sayin' , check the unburned fuel is actually coming out the exhaust !

 

The car is a 2002 model so there's certainly a chance that the tank could have become porous, definitely another possibility. Would be ideal to have a 'sniffer' to actually pinpoint where the stench is originating.

 

I had to replace my fuel tank as it had become porous.

You could smell the fuel with then engine off. If you have a garage, just leave the car in there for 30 minutes - you'll be able to smell the fuel if that is the case.

 

Cheers buddy, I think I can count this out now as I've had the chance to experiment a little while driving to work. I get the smell during a standstill in traffic while idling and the cabin fan on, however once I drive off the smell eliviates as if it's being blown away. This time I isolated the recirc' fan to internal only and low and behold, no smell this time, even at a standstill.

After getting to the staff car park I popped the bonnet thinking that the fuel vapour must be being drawn into the cabin from here and after sticking my nose down the back of the engine, sure enough to I could smell fuel. This concerns me safety wise, fuel vapour around a hot engine can't be good news.

http://www.obd-codes.com/p0420

 

Had a day off today and managed to figure out where the smell was coming from pretty quickly once it was narrowed down to the engine bay. Turns out two of the injectors were weeping, especially the one nearest the firewall.

In case anyone else needs to check this, just remove the plastic cover (two 10mm bolts), energise the fuel system (turn the key but obviously don't start the car) and look to see if it's leaking around the injectors. Mine was easily visible and smellable too.

Honda didn't have the cushion o-rings in stock so I've ordered some to pick up tomorrow at £4.95 + VAT each. Intending on replacing the whole lot.

After thought though - will I likely need any other o-rings than just the top cushion units?

Cheers!

 

Excellent news! You've just reminded me that I have an injector refurb kit stashed away somewhere - it comes with the bigger cushion seals you've got on order and new O-ring seals for the top of the injector to fuel rail (also comes with new filter baskets for the injectors) - so you might want to pick up some of the smaller top O-rings while you're at it.

Also, I've not done this yet but you might want to keep the loom connectors attached to the injectors when you take the fuel rail off as apparently you can drop the injectors at that point in the procedure depending on whether they are stuck in the manifold or the fuel rail (or neither )

 

Interesting thread to read. I'm also running extremely rich at idle and before reading this thread the o2 sensor was the only lead I had.

Thanks!

 

Thanks guys, ordered the o-rings from honda, not cheap for what they are but I'd rather have the peace of mind when it comes to keeping my S fire proof.

I'll put the part numbers in for future ref once I've picked them up.

Thanks for the tip too, Ben. Did some research and noticed someone suggesting leaving the harness attached too. Sounds like a good idea given the hassle incurred if you drop anything inside the manifold

Edit: for anyone reading this later, the top O-rings that seal the injector are part number 16074-ZY3-000 (this is an updated part number, surplanting the old original) and the rubber cushions that sit above the harness are part number 16473-PD6-000. These are not there to keep fuel in the fuel rail and may not need to be replaced.