silvermonster

Hi guys. Been having some kind of issue lately and trying to figure it out.

I have been working with my e-tuner (thinking it might be a tune with flashpro) and he suggested that my o2 sensor might be on its way out. The logs show odd reading from time to time. Making the car run rich. The car died on me a few times in the last month or so. Each time I was able to start it back up. In addition, the CEL light came on and read Rich condition. Since the last reset of the CEL light, it hasn't come back on (about 3 weeks now).

Anyways, I have replaced my primary o2 sensor and it still hows odd sampling. Its creating a odd up and down swings in the o2. The tuner think it might be an exhaust leak right after the o2 sensor itself.

I have a test pipe. I haven't changed or touch anything on the exhaust. This issue came out of no where. Can the gasket on the test pipe go bad? if it leaked a tiny bit, would that cause the primary o2 sensor to behave incorrectly? or could it be a crack in my test pipe that would cause this?

I'll be checking it out either tonight or tomorrow but wanted to see what you guys think. The car runs fine a majority of the time. Any suggestion? Thanks.

silvermonster

anyone experience the stock header developing a crack? or if the stock header gasket has gone bad over time? I never remove the header or done anything to the header manifold. Its all original.

MM3Kwolik

Check/Replace the Exhaust Donut gasket on the end of the manifold. Those are known to go bad and that's what gave me some grief. Once I replaced it, no more codes, and it ran perfect. Hope that helps.

silvermonster

great thanks jordanksartell...what code did it gave you?

MM3Kwolik

I don't remember what the number was, but it was Primary O2 Slow to Respond. The thing is, that donut gasket is somewhat of a flexible joint and when it get's reused, it doesn't compress and seal as good as it should be. It's a cheap part, and pretty easy to replace so it's definitely worth a shot. I'd say that's your most likely source since you say you have a test pipe, and I'm guessing that gasket wasn't replaced when the TP was added.

silvermonster

yeah it wasnt replaced. I just looked it up and will be heading to the dealer to get both gasket. The one in front of the test pipe is 30.73 list price (online is 21.55) and the rear gasket is 8.33 list and 5.83 online.

It does make sense and if its leaking just slightly then it would cause the A/F to be funky.

Found this thread in case someone was interest in it.
https://www.s2ki.com/s2000/topic/598...#entry13442116

s2000maniac

hmmm... i have reused the donut gasket countless of times and havent had any issues.

MM3Kwolik

So have I, but after awhile, they wear out. If there was even a small piece of rust that got wedged in there, it won't seal 100%. It's a (relatively) cheap test to see if that's all it is.