I have tried a number of different cold air intakes for my 2005 Lotus Elise, and while I loved the sound and performance, I have been plagued by the infamous P0171 code that accompanies the inevitable check engine light.
Finally I decided to take matters into my own hand a develop my own solution. The conventional wisdom was that the aftermarket cold air intakes modified the intake pipe size, and MAF sensor location just enough to confuse the Elise’s fragile ECU. This seemed to make sense, as I did have varying success with the aftermarket units, my last one was a simple pipe with a K&N filter clamped on the end. However, the pipe had a slightly larger bore size than the stock air-box.
So, what was my solution? It was simple, I purchased a used Exige air-box and carefully cut-out the enclosed air-pipe using a sharp sawzall and some pliers to clean up the ends. Go slow and take your time. Once you have it removed, find a K&N filter that will fit the end of the pipe, and clamp it down solid. I think you will find that it will solve any CEL issues you may have had, you can say goodbye to P071 for good!
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