Hi guys,

first of all, I would like to apologize for creating a new thread. I assume that this topic was already discussed somewhere else, but I couldn't find it.

The problem:

Roughly a year ago, I've noticed a weird smell from the car which reminded me of some sort of sulfur compound. This wasn't coming from the back of the car, but from somewhere in the middle. I found a leak on the RH test pipe. Got that fixed, but nothing has changed.

I did some track days, autocross etc., nothing significant happened, sometimes during normal cruising the CEL came on with the code

P0140 Rear O2S, Bank 1 High Voltage

This never happened on the track.

Then, my son was born, the car is mostly in the garage and I've used it over the weekends 1-2/month.

Yesterday, after changing the spark plugs, I've noticed a fairly large amount of white residue on the electrodes. Please refer to the image.

Image:




After that, I've done an oil change, installed coilovers and went for a drive. Nothing crazy, just to heat up the car, get everything settled and check if everything's running. After 30 minutes, the CEL came on and these were the codes I got:

P0139 Rear O2S, Bank 1 Response Monitoring
P1146 Heated O2 Sensor 2
P1147 Heated O2 Sensor 2
P1166 Heated O2 Sensor 2
P1167 Heated O2 Sensor 2

I'm getting a strange feeling that there might by something wrong with my O2 sensor/sensors.

Question: Could this be caused by a faulty sensor, or the ECU can't supply more fuel to the system? I have a few bolt ons but IMO the stock Z runs a little bit on the rich side so it should handle it with ease.

Bolt ons that could AFR: K&N Typhoon CAI, Resonated Test Pipes, Invidia Gemini Catback.

Thank you for all the answers.

Martin