I drive an 04 Cooper S with decent modification done to it. I discovered my oem exhaust manifold had cracked at the donut weld just before the cat. I decided to upgrade to an aftermarket header sytem with a test pipe which has been an adventure in itself. After hours of trial and error I finally got everything buttoned up except for one little issue.....my o2 sensors are about 5 inches from fitting in the ports . I have tried previous posted methods such as cutting the wire sheath to free up wire and re-routing sensor but cant seem to get enough slack in the wire. Iv heard of splicing the wires to extend the sensor and have also seen extensions online for "universal use". Does anyone know of extensions that fit our plugs or know if splicing wires to extend them will work? Any help is appreciated.

 

The John Cooper Motorsports manifolds for the Cooper / Cooper S require both oxygen sensors to be extended as it drastically changes their position by a few feet. When I purchassed mine the sensors were no longer included. I was told that the extension should be able to be performed by the dealer. My dealership attempted the extension but it didn't work as the aft sensor kept triggering a fault code. I ended up paying to have some shipped pre altered from the UK as they're familliar with the process. But even the ones from the UK are just cut and soldered now. So it's definately doable and mine work code free.

 

Not sure about splicing the wires. I suppose as long as you use the correct wire gauge, solder, and wrap with a heat shrink it should be okay. Don't hold me on that though as I have never tried it. You can always take it to a muffler shop and have them weld a bung closer to the sensor. Shouldn't cost a whole lot.

 

So after a lot of thought I decided to tackle the extension myself. I heard a lot of rumors about ohm resistance and was nervous about splicing a sensor but took the dive anyways. Part of it was my laziness for not wanting to take the header off...I basically pulled back the heat sheath from the wires and spliced about 7 inches from harness next to the air box. I used water tight heat shrink crimp connectors. I was instructed by the dealer that solder would not stick to the existing o2 sensor wire and that the proper way to do it is crimping. After crimping and heat shrinking the the new connections I added another heat shrink on top of each connection as extra insurance one would not come loose on me. The oem heat sheath would not fit over these new connections so I purchased a 5 foot roll of hose heat shielding from summit racing and put the whole thing inside on of these tube heat shields. I now have plenty of room without stressing the wires. Everything is working properly and car runs great. No issues so far. Definitely take your time if doing this yourself but it is doable. Thanks for your guys help.