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Discussion Starter · #1 · (Edited)
I have been having trouble with my 2005 Elise for about three months now. There is a seperate posting regarding the CEL that came and some of the diagnostics I tried to clear the P0171 (mixture too lean) code.

Since then I have had a mechanic friend of a friend take a look at the car and we tried all the obvious things (MAF, O2 sensor, checked for intake system leaks (he even used a smoke system that you put inside the engine that creates positive pressure to check for leaks), cleaned the injectors, checked the fuel pump pressure, we tried reducing the diameter of the intake by putting a spool piece inside it ... none of this cleared the problem. At this point I have to give kudos to my mechanic friend who did all of this in his spare time and basically charged me $100 for his time spread over 6 weeks :clap:

However, we still had the same problem. Whenever we ran the car over 3-4K rpm, the ECU would throw a 'pending' P0171 code, then next time you started the car a full blown P0171 code would be thrown and the CEL would come on. We worked out that this is because the subsequent engine start is the second drive cycle and hence the very next pending code is combined with the existing pending codes to throw a CEL.

My mechanic buddy was out of ideas and needed the Lotus specific scan tools to get more information, so we took the car to our local dealer (Motorcars of Georgia). Now I am not a fan of dealers but I must give the mechanic (Roman) at Motorcars of Georgia credit, he basically swapped parts between my car and another 05 they had in stock until the found a problem. When they changed out the ECU the problem cleared itself. They then put my ECU back and the problem came back. It seemed pretty obvious that the ECU was the culprit. The Motorcars of Georgia guys tried to reflash my ECU and could not get the updates to take, they said the ECU as damaged and sold me a new sport ECU to replace it ($875)

Now reading one of CharleX's old posts, it may just have been that they did not have access to the correct tools to do a complete reset so I may have ended up buying a new ECU when CharleX may have been able to reflash it for me.

I drove the car for a couple of days, no CEL and it ran great. Then after a couple of days the CEL came back on again (same basic code and pending code). I took the car back to the dealer and they have now checked the code and lotus sub-codes. They have then discussed this with Lotus USA who say the Lotus specfic sub-codes indicate that the ECU is unable to learn because the air intake is out of tolerance and the recommendation is to put the stock intake back on. I purchased the car used about 10K miles ago and it had the TurboXS intake on at that time. I have since spoke to the orginal owner who had the TurboXS intake fitted and he ran it for approx 20K miles with no problems. Hence I am a little hestitant to spend the $1000+ that they want to supply and install the stock airbox.

I guess my main question is to CharleX or other ECU experts - is there an after market reflash that will modify the ECU for use with the higher air flows of the TurboXS intake - if so which one and how much $$

Also, am I better off spending much less than the $1000+ for the stock intake and purchasing a different aftermarket CAI (I have read many postings about the TurboXS causing P0171 CEL codes).

Any other comments would be welcome.
 

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I've seen people selling the stock airbox for cheap, sub $300, on here.

I don't know particularly much about the intake problems you're having, but I hear the k/n intake is supposed to work pretty well, according to Charlie.
 

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Cup car is the best IMO
 

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Tossing a CAI on should not cause any kind of lean condition. I would suspect that something else is going on, either a problem with the AFM, or a vacuum leak letting unmetered air into the system somewhere, even with all the diagnostic stuff you tried.

It shouldn't matter how much air everything in front of the AFM flows. You could run the car with an open AFM and it should not make any difference to the computer. The only thing that should matter, and the only thing to my knowledge will cause the lean code, is if the o2 sensor is in fact reporting a lean condition. The only causes for that, assuming the o2 sensor is operating properly, are:

- Leak in the induction piping after the AFM.
- Malfunctioning AFM.
- Fuel pressure or injector flow issue.

Any AFM issues should throw a code in addition to the lean code, so if that isn't happening, the unit itself is probably fine, and it's an indication of an air leak or fuel problem.

You mentioned the fuel pressure was checked-- have the injectors ever been cleaned? How many miles are on the car? You may want to have the injectors cleaned/flowed (preferably off the car) and see if that affects anything. RC Engineering does awesome work in that regard.
 

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The sound alone of the Cup airbox makes it better. I have no idea if it adds any HP but it bolts on, doesn't cause CELs and adds and read +10 hp on the butt dyno for me :D
 

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The sound alone of the Cup airbox makes it better. I have no idea if it adds any HP but it bolts on, doesn't cause CELs and adds and read +10 hp on the butt dyno for me :D
Chances are low to no hp gains, but if your old filter was really dirty, you would feel a difference.

And yeah, the sound is amazing :panic:
 

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Discussion Starter · #9 ·
Thanks for the responses. I guess my thread is going to two directions, 1) CAI - remove it and go stock or put on another aftermarket model -OR- 2) is there anything wrong with the ECU and do I need a reflash to handle the TurboXS intake.

1) The CAI has been on the car for about 30K miles so I am very reluctant to accept that this is the problem. That said I have tried everything on the air side except replacing the intake. Anyone out there got a stock airbox laying around that I can try :)

2) I am very concerned about the local dealer's orginial assertion that the ECU was 'damaged' and beyond repair. Only for the car to code with the same symptoms 2-3 days after replacing the ECU. The dealer is now saying that the ECU cannot learn because the flow being seen by the MAF is out of tolerence - can this be true? Does a default ECU go throug some initial learning that it needs to completed with the stock airbox before an aftermarket CAI can be fitted?. I am a little hampered by the fact that I do not have the specific sub-codes that the dealer says their scanner read so was hoping that someone in this forum might know if this story sounds true and arm me with enough info to talk to the dealer from a knowledgable point of view.
 
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