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Discussion Starter #1
Not sure if this is an intake question, or a general maint & repair question (I apologize in advance if I have posted in the wrong Forum).

Anyway, I have a 2005 Elise, approx 40K miles wuth a TurboXS after market intake. I have had the car for just over a year and do most of my own maint. The other week the engine light came and after getting a scan of the OBD code I found that it was reporting P0171 (Mixture too lean).

I tried cleaning and re-oiling the K&N filter on the intake and then sort of cleaning the MAF (I inspected it and blew off any dust - it looked very clean). I cleared the code and ran the car for about 15 mins on my driveway and the light stayed off. However, once i backed it off my drive the light came back on (same code) immediately.

I am planning on cleaning the MAF completely (using some brake fluid), but wanted to get some additional input regarding whatelse to try. Also does any one know a viable way of testing the MAF to know if it is damaged (I dont want to spring for a $150 sensor if the problem is elsewhere).

Also I have a track day scheduled for this Friday and dont want to run if the engine is truely running lean - any thoughts on this?

TIA
 

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Pull the plugs, lets see em here. Try getting your gas from the same place every time, preferably a premium station(Chevron, Shell) helps rule out a batch of bad gas.

Try a bottle of octane boost(Or a half tank of race gas), see if it throws the code after that.
 

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Use MAF cleaner on your MAF, I found it at a auto parts store.
 

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Discussion Starter #5
Pull the plugs, lets see em here. Try getting your gas from the same place every time, preferably a premium station(Chevron, Shell) helps rule out a batch of bad gas.

Try a bottle of octane boost(Or a half tank of race gas), see if it throws the code after that.
Thanks for the advice, I will be pulling the plugs tommorrow and will post pics. I was thinking of trying a bottle of Injector Cleaner or would you think octane boost / race gas is better.
 

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Discussion Starter #6
Anyone up for some further diagnostics ? ... I am not sure I am ready to give up and take the car to a dealer just yet.

Here are the details:
2005 Elise, about 40K miles, purchased used about 2 years ago, only engine mod is TurboXS intake. Car has been tracked both by me and the prior owner

Problem:
About a week ago the CEL came on as I was backing off my drive. I purchased a inexpensive OBD reader and determined the code was P0171 (mixture lean). Since then I have tried a number of different things to fix this (see below). Using the scanner I have confirmed the following:
1. CEL comes on whenever I start the car from cold. I can back the car off my driveway CEL comes on, I then immediately reset the code and can then drive to work without the CEL coming back on. When I get ready to come home the same thing happens.
2. The reader displays what they call 'pending codes', basically an error that has been detected, but it has not happened enough times (yet) to set the CEL. Using the reader I have comfirmed that I get a pending P0171 (mixture too lean) code whenever I rev the car hard (say >5K). I am assuming that if I kept the car at high revs for long enough I would get the full blown P0171 code and the CEL would come on (I haven't checked this yet ... my drive to work will not allow this and I am not sure my nieghbors would appreciate me sitting on the driveway at 9:00pm with my foot on the gas for 10mins).

Heres what I have tried so far:
1. Cleaned and re-oiled the filter (K&N)
2. Cleaned the MAF
3. Added a bottle of injector cleaner to the tank, but I have only run through 1/4 of tank since I did that.

My thoughts are that the air side of the air/fuel mixture seems like it checks out. I guess I need to start on the fuel side. I am thinking that if the car throws CELs when cold and warnings at high revs, it may not be getting enough fuel.

Anyone have any suggestions where to start on the fuel side, fuel filter, fuel pump, injectors ??? and also can you point me to any instructions or service manuals detailing how to remove / check these items?

The other area I am considering is the O2 sensor, any thoughts on how difficult this is to change, is there anyway to test it without just changing out the part.

Thanks
 

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what did you clean the maf with ? did you make sure you didn't over oil the filter that'll cause the maf to get contaminated ?

if you have the stock CAI put it in and let it run for 50 miles and see if it still happens.
 

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Discussion Starter #8 (Edited)
what did you clean the maf with ? did you make sure you didn't over oil the filter that'll cause the maf to get contaminated ?

if you have the stock CAI put it in and let it run for 50 miles and see if it still happens.
I do not have the stock intake setup so cannot go back to that.
I do not think I over-oiled the filter, I have cleaned and oiled it before and I do not think I put any more oil on it this time. Also I cleaned the MAF about 2 days after I have oiled the filter, so I assume that this cleaning would have got rid of any excess oil. I used brake fliud to clean the MAF.

Thanks
 

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Thanks for the advice, I will be pulling the plugs tommorrow and will post pics. I was thinking of trying a bottle of Injector Cleaner or would you think octane boost / race gas is better.

Race gas/ higher octane fuel should richen up your A/F ratios, thus curing a lean condition. So, if you dont pull a lean code on higher octane fuel, then you can just keep running octane boost instead of replacing your aftermarket intake.


This is correct, right charlie? Or am I confused?
 

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I have the Fujita intake and if my air filter gets even "damp" it throws the lean code, I do not oil the filter at all, if there is anything moist about it the CEL will throw that code.

Todd
 

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Discussion Starter #11 (Edited)
Race gas/ higher octane fuel should richen up your A/F ratios, thus curing a lean condition. So, if you dont pull a lean code on higher octane fuel, then you can just keep running octane boost instead of replacing your aftermarket intake.


This is correct, right charlie? Or am I confused?

Are we suggesting that the lean code is just a fact of life with the intake and the ECU is just being overcautious? Also, does it matter that the engine has run for 10K miles (that I know off) with this intake and the problem just started last week. I guess I am concerned that there is something else wrong.

I noted that you had previously suggested checking the plugs. I just pulled these and checked the gaps (1.1mm). I have posted pics for you to comment on.
 

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don't clean your maf sensor with brake fluid use non residue leaving contact cleaner or a maf cleaner which is usually contact cleaner that costs more.

its a pretty common code for CAI's, check the short term fuel trims.
 

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Discussion Starter #13
I just pulled the filter and it is very heavliy oiled, in fact there was filter oil dripping into the wheel well (looks like I wasn't paying attention :wallbang: when I cleaned and oil it).

On the subject of using break fluid to clean the MAF, could this have damaged the MAF ??

Thanks
 

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Discussion Starter #14
don't clean your maf sensor with brake fluid use non residue leaving contact cleaner or a maf cleaner which is usually contact cleaner that costs more.

its a pretty common code for CAI's, check the short term fuel trims.
In reading this (and other forums) I hear of lot of mention about the 'CharleX ECU mods' ... are these only for supercharged cars, or do you have a specific mod for the type of intake problem I may be having.
 

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yeah i can fix that.

the maf sensor is probably got some residue on it since its a hot wire, if so it'll be forming an insulator between the air and the sensor, brake cleaner may have stripped it too.

if it idles badly the maf might be fubar'd, otherwise clean it up with maf cleaner.
 

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Discussion Starter #16
Thanks for all the help so far.

I have cleaned the MAF (using contact cleaner), I have dried out my over oiled filter, I have added a bottle of octane boost (and run about 1/4 tank of gas). However, I am still getting the CEL light coming on when starting from cold and the pending 'mixture lean' code at high revs.

My next steps are:
1. New plugs - I posted pics of the existing ones, they looked a little blackened, anyway it takes 10mins (OK so I am slow :rolleyes:) and will only cost $20.
2. New MAF ... I hate to do this since it is going to cost me $150 or more and I just have this gut feeling that it is not the MAF. But I bow to the advice of more experienced people than I :bow: and will try this.

Assuming these changes do not work I guess I have a couple of choices:
1. Just accept that with this intake you get these lean codes, ignore the CEL light and check using a OBD reader every couple of weeks to determine is I have any new trouble codes.
2. Keep digging ....

Assuming I keep digging (likely since I am pretty persistent :wallbang:) and I am still having a hard time accepting that the car has run for at least 10K miles (maybe 30K) with this same intake setup and not thrown any CEL's.
Do I change out the O2 sensor, if so which one? (or both?) - also where is the second one? (I can find the one visible as you remove the rear left wheel and inner wheel well)
Or would I be better admitting defeat and going to a dealer (or other) and having them at least run a full scan using their $5K OBD scanner?

Thanks
 

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I ran the TurboXS intake for a while and two cases where the P0171 code popped up. In both cases, I loosened the clamps holding the tube between the MAF and the throttle body and reseated everything before retightening the clamps. I also made sure all the unused vacuum tubing was securely plugged.

That fixed the problem both times, but I make no guarantees that it wasn't just coincidence. I eventually ditched the intake as off-idle throttle response seems a whole lot worse with it as compared to the stock airbox.
 

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Before I installed my S/C I had a Fujita intake installed. I never had a CEL with it but as I understand a lot of people did (lean condition I believe). As I recall it had to do with how far the the filter was pushed onto the intake, thus the length of the intake prior to the MAF?
After I went to my S/C I then got a dirty MAF, (no CEL but rev limiter kicked in) not sure if it was from the Fujita filter or K&N filter. Fixed it by cleaning the MAF, I have not cleaned my air filter yet (<10k miles).
 

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Before I installed my S/C I had a Fujita intake installed. I never had a CEL with it but as I understand a lot of people did (lean condition I believe). As I recall it had to do with how far the the filter was pushed onto the intake, thus the length of the intake prior to the MAF?
After I went to my S/C I then got a dirty MAF, (no CEL but rev limiter kicked in) not sure if it was from the Fujita filter or K&N filter. Fixed it by cleaning the MAF, I have not cleaned my air filter yet (<10k miles).
Here's the big question, how far on is the right amount? I just did my Fujita last night and only put it on about an inch (length of that little lip on the cupler) and then 100 miles later I threw a CEL.
 
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