New O2 sensor, and a strange burning smell

[rjd2]

Hi all, so in the hunt for the cause of my high idle(2000-2500 RPM), I replaced the O2 sensor, as this was mentioned as a possible cause. I had a fairly easy go at the job, however, when I started the car upon completion, I got a strange burning smell(it also did not solve the idle issue). It was definitely not the usual smell to me; it was similar to burning plastic, as far as smells go. I do think I could notice a bit of gray fumes or whatnot that is not usual. Any thoughts on that? Is there a normal "burnoff" period or anything that I may not be aware of? As an aside, I have a hunch that the mixture is set rich. Thanks for any thoughts!

[DMC-81]

I didn't notice a burning smell when I replaced mine. Mind you, I had some smoke and smell as I was curing Hi Temp POR -15 exhaust paint at the same time. But definitely not a smell of plastic.

Was there perhaps a plastic cap on the sensor end that didn't get removed or was the wire routed too close to the exhaust pipe?

[rjd2]

I didn't notice a burning smell when I replaced mine. Mind you, I had some smoke and smell as I was curing Hi Temp POR -15 exhaust paint at the same time. But definitely not a smell of plastic.

Was there perhaps a plastic cap on the sensor end that didn't get removed or was the wire routed too close to the exhaust pipe?

Thanks for the response. There was not a plastic cap, and i know the wire was threaded through the frame properly, and isn't laying against the exhaust. The car only ran for about 30-60 seconds, so I doubt there'd be enough heat generated at the exhaust to melt anything....

[Jonathan]

The smell is probably related to the mixture being too rich.

The original idle problem being up around 2,500 RPM is probably a bad electrical connection on the thermistor, which is located under the intake in the valley (which admittedly sucks to need to go in there to correct it).

[rjd2]

The smell is probably related to the mixture being too rich.

The original idle problem being up around 2,500 RPM is probably a bad electrical connection on the thermistor, which is located under the intake in the valley (which admittedly sucks to need to go in there to correct it).

This would, unfortunately, make sense as that problem introduced itself immediately after the thermister job. I distinctly remember doing my best to make sure the harness on the actual thermister secure before re-assembly. Is there a physical way to check that without doing a full disassembly, down to the valley? I keep wondering if there's a way to get a go pro camera down in there or something with my arm, just to check that harness. The idle jumps around erratically; if I let it sit, for a minute, it will occasionally just jump from 2000-2200 up to 3000-immediately-without any physical touch to the throttle at all. I think the prudent thing is for me to go back and double check all my connections....sigh...

Thanks for the help!

[NckT]

Assuming that the hammer on the throttle presses the idle microswitch, remove the white multi plug that has 4 wires on it. Use a multi meter, set the resistance k ohms and put the multi meter probes on the black/yellow and black/slate (grey) wires at the multi plug. If you get no reading ie open circuit, then you have a wiring problem to the thermistor. In this case, you could refit the white multi plug and put a 10 k ohm resistor across these wires effectively fooling the Idle ecu that it is referencing the thermistor.

Let's hope that the idle motor doesn't have a short or that the ecu had not blown one of the switching transistors that operates the motor etc

Good luck