Update: 3/17/2014 – The sensor has come on twice since installing this “hack” or fix. It seems like it’s still able to build up some residue or buildup on the sensor and trigger the light to come on after about six months of use. I will be giving the Blackwatch Racing MIL Light Eliminator Kit a shot and will report back on my success or failure.
Update: 12/30/2010 – between 400 and 500 miles on the vehicle and the check engine light has not come back on.
So I’ve done a fair bit of research on how to eliminate the check-engine light when you remove your stock catalytic converter and either replace it with a test-pipe or a sports-cat (which I believe is basically just a small muffler, but I could be mistaken). My CEL didn’t come on until about 20 minutes after replacing mine and it never went back off.
I searched around LotusTalk for a solutions and found different “mil mods” and “o2 defouler” solutions. I decided to try the cheapest and most readily available option first and see if that worked.
I went to Autozone and picked up a set of 18mm Oil Non-Foulers from the Help! section. The part number if you want it is 42002. I made the mistaken of buying smaller 14mm non-foulers first and they didn’t fit. These are the old-school non foulers used on older Ford pickups etc. O’Reileys didn’t have them when I was there with a friend later showing him what I had bought. They did have a Help! section but no non-foulers. Could’ve been just the store though. A few guys at LT have said they tried this and it didn’t work. I’m wondering if they did it right or were able to screw the O2 sensor in far enough to make it work properly. If you have tried this and it didn’t work – make sure you’re able to seat the O2 sensor all the way in to the non-fouler. It would make no sense why it would work for some people and not others on the same vehicle.
You’ll want to take one of the non-foulers and drill it out with a 1/2″ drill bit. You may want to start with smaller bits and work your way up to make sure it’s centered and doesn’t go in at an angle or spin off the top and mess up the threads on the side. At first, this only screwed on a few threads to the O2 sensor so I took my dremel with a sanding/grinding tip and even further removed the inner “lip” area and made it deep enough for the Lotus’ O2 sensor. I then screwed the other non-fouler onto this one and screwed the O2 sensor into the one I had bored out. When you’re all said and done this is what it should look like (Note: This is not an Elise, I just didn’t have a camera with me when I installed mine so I found this one thanks to google images):
So keep in mind – if it doesn’t fit, bore it out a bit more from the inside. A few guys at LT have used a 5/6″ bit to drill theirs out but I felt more comfortable with a dremel.
I then cleared my check engine light when was something like an “emissions threshold” and I waited until the ECU had run it’s emissions checklist again and it had completed and passed. A 3 hour roadtrip later and my CEL was still off. Let’s hope it doesn’t come back on! Seems to work so far, I’ll keep this post updated with any information on this if anything changes.