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Discussion Starter #1
2005 stock Elise, 31k miles, I did most the 30K routine maintenance within the last two months. It ran normal until this morning. When I got up to go to work, turned the key and the CEL came on and remained on. I went to Autozone after work and got a Code P0171 read out. The print out as follow:

air/fuel mixture system lean bank 1
(cylinder number 1 denotes bank 1)

Probable cause:

1) low fuel pressure
2) faulty MAF/VAF sensor
3) cylinder misfire condition
4) faulty H02S/AF sensor
5) large vacuum leak

This afternoon, when I pulled it out of the garage to Autozone, initially, I heard some "extra noise" from the back. It sounds like suction noise but only last a few seconds and gone. The car felt normal.

Since Feb. 2012, ~30Kmiles, I have done the following to the car:

--Feb. 2012 @ ~30.5K miles, changed spark plugs, iridium (NGK BKR6EIX-11).

-- early April 2012 @ ~ 31k miles, changed coolant, brake pads/ flush brake system, transmission fluid, and reinstalled Fujita CAI (uninstalled at ~15K miles after ~ 1k miles use secondary to "feel too loud" at that time).

The odometer now reads 31,250 miles, I have not used up the first tank of gas since above changes. Projected MPG about 25, same as last 15k miles.

Given all these probable causes, and my limited mechanical knowledge/skill, how should I approach this issue??

I also have these questions:

Is there any other cause(s) that might light up the CEL??
Standing at the rear of car facing forward, is cylinder 1 the one on left or right?
Is HO2S = O2 sensor? MAF sensor = AF sensor?
Is the car safe to drive with the CEL on??? Will it hurt the engine in anyway??

I apologize for the primitive questions and thanks for all the help in advance.
 

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Discussion Starter #3
CEL off

I drove the car to work this morning with CEL still on. Planning to pick up some MAF cleaner on the way home. When I started the car after work, the CEL was on no more.:nanner: I have not done anything to the car yet and do not know what had triggered it off. I will post again if it comes back on.

Thanks for the advise.
 

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What brand fuel are you using? Shell has additives which will trip a P0171 code on the Esprit V8. It's a false error but it happens consistently. The Elise ECU tuning may be the same. I switched to Chevron and have never seen one since on the V8. I've never used anything but Chevron in the Elise and have never gotten such a code in 38K miles.
 

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Is the CAI oiled? If so I am betting its your MAF. These cars are notorious with oiled filters due to the MAF sensor sitting in the actual filter housing. Most cars the MAF is downstream further in the middle of the intake tube between the air filter and the TB.
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shay2nak
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just because the CEL is off doesn't mean it's fixed. The code you tripped is still in memory.
 

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I have a spare used MAF if you end up needing one. I recently replaced mine due to a CEL but it turned out to be the o2 sensor.
 

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I'm a bit late on this response but no, I ordered them from LotusGarage.
 

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Crusader thats a different code a gas cap would be an 044 code. If you had it there are other things happening. I would say it is the fujita as there have been countless threads on it back in 05 and 06. Simetimes it clears sometimes not.


Sent from my Autoguide iPhone app
 

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you can get that same fault for not closing your gas cap properly.
No. Gas cap is an evaporative code. P044x...I can't remeber if it's 440, 442, or something else.

When I had p0171 it was an O2 sensor. See if you can read feedback for the oxygen sensors from the scanner. Pretty easy to tell if it's an oxygen sensor that way. Good luck!
 
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