O2 sensor heater wiring 12V backfeed DIY

[boyd_dave]

After a year with the swap, i'm not entirely convinced this mod was necessary. What ultimately seemed to help the most was to move the o2 sensor closer to the engine along the headers. I moved it 12" closer and it now operates with no issues and has for over a year now.

If the o2 sensor is just a bit too far away from the engine to get good heat, it will not work properly even with correct wiring.

[DREWHALL]

To bring this thread back into light, I have been wanting to investigate this further on my car. It occasionally has a surging idle. I started looking into my harness, the green/violet wire you are showing the modification being done to, is already powered by F11/Fuel Pump on my car. I never have a CEL when the idle starts acting up, and if I plug my ICV in the idle just goes nuts. Most likely a separate issue I am yet to diag, probably just the ICV. I will say that I adjusted the idle set screw on the throttle body and that helped. The idle would hang around 1100 and that's when it would drop off sharply then raise back to 1100 repeatedly. After adjusting it doesn't do this.

[hwy84]

To bring this thread back into light, I have been wanting to investigate this further on my car. It occasionally has a surging idle. I started looking into my harness, the green/violet wire you are showing the modification being done to, is already powered by F11/Fuel Pump on my car. I never have a CEL when the idle starts acting up, and if I plug my ICV in the idle just goes nuts. Most likely a separate issue I am yet to diag, probably just the ICV. I will say that I adjusted the idle set screw on the throttle body and that helped. The idle would hang around 1100 and that's when it would drop off sharply then raise back to 1100 repeatedly. After adjusting it doesn't do this.

Plugging in the ICV after having it disconnected will cause idle to go from about 500 RPM to roughly 2,000 RPM for about 30-45 seconds as the ECU learns the extreme ends of the ICV open and closed positions. Wait it out. It will settle in.

[DREWHALL]

That's what I was hoping, but I wasn't sure and it was annoying. Thanks for the tip.

[eurosport22]

so i was looking through these o2 threads and have been putting off doing it because my m3 harness covers are a bitch and a half to get back on. but ii was thinking, would you be able to draw power from one of the 2 accessory fuses that are in that little box by the main fuse box. isnt one of them switched and one always hot? has anyone done this instead. it would keep the box neater and allow the cover to go on nicely.

[88E30M50]

I just did this mood over the weekend and it made a huge difference in how well the car runs. It no longer stalls when you lift off the throttle after a bit of a run. Thanks for the info guys.

Tim

Sent from my HTC Glacier using Tapatalk 2

[dcskate102]

Didn't work for me, the car wouldn't even start

[OrganicMechanic]

glad this helped...