Can i change both of the o2 sensors? can the one in the cat be removed? and where in the exhaust manifold is the other one located?
can someone post me a pic if there's one? thanks.
PS Can i change the cat with another one? i think i might be able to do that! Is it an easy thing to do? is it just plugged or will we have to cut it or something?

 

Sorry, no pics that I can think of. I'm not sure that the primary (in the header) and secondary (in the cat) O2 sensors are interchangeable. They both just unscrew like a spark plug although most O2 sensor tend to get partially seized, so use some penetrant first. The one in the cat is sticking out the left side about mid-way along the cat. The one in the exhaust header sticks out the right side after where all the individual pipes come together. Once you unscrew each sensor, you need to trace the wiring bundle to the harness and you can disconnect them at the harness. Getting at the harness connection might be the most difficult part.

 

Thanks for the info Xviper.
I actually dont know what to do. What would you do next?

 

That's a tough one to answer since it's not a situation I've ever encountered. If it were my car, I'd have the ability to have "hands on" with it and listen, feel, and experiment with different things. Not knowing exactly what your car sounds like, feels like, or runs like is very difficult to add any more than what's been posted already. I suppose if it were me and I'd have run out of ideas, I'd just take it to the dealer and leave it with them till they got it right. But you've done that and they tell you nothing is wrong. So, from 1/2 way around the other side of the world, all I can say is, if they couldn't find out what's wrong, the rest of us have much less chance on it given that we can't see the car, drive the car or listen to the car.

 

Now I have a question for everyone???

What if someone (previous owner ) has somehow disabled the ability to "throw" a CEL??? Now, I don't know how someone would do that "computer-wise" within the S2000, but maybe they've "fiddled-with-the-dash-idiot-light" so that it doesn't throw on the dash???

Cyprus...why don't you do this (and someone offer an "easy suggestion" here) : Why don't you *deliberately* create a situation that should throw a CEL...and then wait and see the results?

Is this a fair suggestion?

 

Interesting concept. If the "BACK UP" fuse was pulled and left out, no CEL would ever come on AND the car would run very strangely, but you'd think that when the car was in for full diagnostics, they would have picked up on that. However, I do recall he said he has reset the ECU several times, so the fuse must be there.
A simple way to get a CEL would be to unplug the VTEC solenoid wiring harness (that's the one sticking out the side just under the little VTEC cylinder), start the car and the CEL should come on within a few seconds.

 

Well, what w1ingman said makes sense, but i changed the ECU.
If the previous owner did such a thing, he would have done it with the ECU init? I changed the ECU so i dont have to worry about that now do i?
Another thing is, i dont reset the ECU by pulling the backup fuse out. I reset it by removing the + cable off the battery, put the key on, turn it, act like starting the car (push the engine start just once), remove the key and wait for 3 minutes. The ECU resets. It does right? bcoz the radio and all that gets reset. And one interesting thing, after i reset the ECU, for like half an hour drive or something, when i press the clutch when i'm moving, the rpm comes down to 200 instead of 900. It feels like the car's gonna turn off. After half an hour or 20 mins, back to normal. Than the problem starts. Shit world!
I should check the ecu backup fuse init, but if it wasnt there, the ecu would reset everytime i turn off the car init? so its there. My problem is kind of mechanic i think. No CEL ever, nothing wrong in the computer, so it makes me think it's mechanic. If it was something about the engine, wouldnt it do it all the time? or like my mechanic said the problem is gonna go away after some time? i dont know what to think like i said before, i thank all of you people for all the suggestions and the help and the support, but please i do really need some more help.

 

I'll find some pics of the fuse and check it anyway.

 

Hey XViper, I'm the other guy thats having these same issues....Both of use are experiences these gurgling, slight backfire noises from the exhaust too. Muscle car engines due this due to their cams.... now..... Maybe there is something wrong with our timing, like maybe our exhaust cam could be undertimed or something? I spoke with a Porsche mechanic, and he pointed that out. Could this be an issue, the timing? Another point... I am having similar problems as Cyprus with the clutch. I am no mechanic, I am just restating what the Porsche guy said, haha.

 

Yes, do check that the BACK UP fuse is there and is good. If it were missing or if it were blown, the car would act in the fashion you have been describing. I'm not sure that it would ever run right as you say, but this ECU is very adaptive and I suppose given enough time, it might even compensate for something as stupid as having no BACK UP fuse.
There is a much simpler way to reset the ECU. You just pull the BACK UP fuse for 30 seconds and put it back in. No need to mess with the battery or the key or anything. You've been doing it the hard way. I'm not sure but without this fuse, you could be really messing up the way the ECU works by undoing the battery and messing with the key like you have been.
Here are some pics to help you find the BACK UP fuse: