Intermittent Check engine light, O2 sensor

[JimEE]

I have a 2000 Boxster S, 6 speed, with 30,000 miles. Just before my 30k inspection, my check engine light came on and stayed on (steady not blinking) for the 4 days or so until I got it in the shop (Porsche dealer). Dealer said the readout indicated a bad O2 sensor, but he checked it out and it was OK. So, they didn't replace it, and reset the readout and did the rest of the 30k inspection.

About a week after the 30K inspection, the light came on again. But I kept driving it (it was steady not flashing), and I figured I'd need to go in and get the O2 sensor replaced, and made the appointment. But then the check engine light went out. So, I cancelled the appointment.

Drove another week and all was fine. But then, the check engine light came on again (steady, not flashing). I drove it that way for a week.

My normal driving to work is all I was doing, but that driving is mostly in the 30mph range, as I don't get on a freeway. So, I thought maybe the slow driving was causing the O2 sensor some problems. I went out on a 25mile freeway romp about 80mph in 4th gear, keeping the rev's around 4k or so. The light was still on. Next day I went to work, light still on, but then, after work, the light was off.

I seem to notice that when the chk engine light is on, my car runs rougher, if it's cold (just after starting).

Now, maybe all these chk engine lights are for the O2 sensor and maybe not. I'll have to bring into the shop to find out.

But, has anyone ever experienced this intermittency?? I'm thinking it might be a connection instead of the sensor itself, since past experience in all things electrical/electronic often indicate connection issues when the problems are intermittent.

Thanks, Jim

[Loren]

Without the fault code(s) everything is just a guess.

Go to an Autoszone (or other auto parts store) and get your codes read.

Write them down and report them back here.

[mikefocke]

Good news is anyone who can get under the rear can change one for 25% of dealer cost

Part numbers and how to here