So, driving from Miami to Jacksonville and after about 3 hours of freeway driving (80 mph on cruise) I get a service engine soon light. check the code and it is P0171, fuel mixture lean bank 1... Two questions; How bad is this, and can I fix it?

engine/exhaust mods are:
-Buschur racing Upper IC pipe, FMIC, and cat-back exhaust
-AEM intake
-Speedckt mail-in ecu tune (med)

its the ecu tune, its ment for a factory set up basicly leans out the car and with the exhaust and intercooler pipeing its running too lean. are you getting any knock or are you haveing trouble with engine temp?

the code is system lean bank 1. People have reported problems with mass air flow sensors. A faulty mass air flow sensor could cause this code. Or your fuel system is actually leaning out.

1) This code can happen if you fuel the car without turning it off or do not tighten the gas cap tight. It can also be thrown by HFC or Test Pipe. It could also be from the leaning out of the car from tune, intake and Fmic. Talked to Perrin about this, and it really should not be a problem. I would call the guys you have gotten stuff from. Dino could probably answer questions. Do you have a test pipe or high flow cat? If yes for the last 2 get a defowler or extender for the O2 sensor. If that doesnt work I hear the Accessport can clear up these issues.

So, after noodling for a bit I realized that I took a trip to Orlando with no problems about a month ago. The only thing that I changed is I put the BR "Quieter" muffler on. Would this make any difference. Oh, and another thing I did not mention is it happened on the trip up and down, but only after about 3 hours of hwy driving followed by a gas fill up and getting back on the hwy. I filled up in jax and back home with out any problems.

no your muffler shouldnt have played a part in you being lean.

Did you fill up at the same gas station on the way there and back? perhaps poor quality fuel? ( did you use 93?)

A lean code can not be set by filling gas tank with the engine running. You would only get a evap system leak code from that. Also you would not get a lean code from a high flow cat or test pipe. The only code you would get from those is a cat efficiantcy code. The ecu will through a lean code based off of the readings from the upstream or "front" o2 sensor. The cat or test pipe will only affect the reading of the rear o2. You either are running lean due to the tune, you have a vacuum leak or possibly a bad mass air flow sensor. People have reported having problems with mass air flow sensors so that is a good possibility.

^I was told by multiple people that this could be thrown by filling the car while engine is running or by not tightening the gas cap. All of these people are fairly reliable. But Im sure it could be from what you say as well. I didnt get this code till I put on a turbo back exhaust, and have not gotten it again since I placed a defowler on the car.

not to sound rude but i dont want bad info out there either. who ever told you that info is incorrect. i have been a mechanic for the last ten years. a.s.e. certified. a p0171 code can not be caused by the fuel cap.

^I wouldnt know as I am no mechanic so I will just have to go off what you say. You cant really offend me. Im learning as I go.

The code is definitely not a result of the tune. The EcuTeK currently cannot control closed loop, therefore the air:fuel ratios you run while you're cruising are tweaked on the fly via the car's sensors to 14.7:1.

If you were in open loop and driving spiritedly when this occurred, the tune could be at fault. However, that is not the case here.

Well lucky me I just got this code to. Installed an AMS intake and UICP about 2 weeks ago or so and now all the sudden a CEL comes on with error code P0171.....

I have already checked everythign to make sure nothing is loose etc... but at this point I see nothing that would cause this.

This is on an otherwise stock car with 2,000 miles total.

All I can think of based on this thread and my prior knowledge is something is up with the MAF sensor.

I want to bump this for some answers if anyone can help me out. I reset the CEL i was having and after driving about 50 miles is is back on. Still get CEL code P0171 "system to lean".

I checked all hoses, connections etc...and everything is fine. The car is 100% stock other than the intake and uicp. I plan to call AMS to ask them what their thoughts are.

I searched the forums and everyone else that i can see that has gooten this CEL has a tune. I only have an intake I just don't see how that would cause this code. My car also only has 2000 miles total.

Anyone?

try a dif MAF do you have a friend that has a lancer or eclipse? cuz the MAF is the same.

I would look for air leak past the MAF sensor, or dirty MAF sensor which you can clean with brake cleaner. However since the car is so new I would go for an air leak somewhere.

try a dif MAF do you have a friend that has a lancer or eclipse? cuz the MAF is the same.


good idea but no i don't

I would look for air leak past the MAF sensor, or dirty MAF sensor which you can clean with brake cleaner. However since the car is so new I would go for an air leak somewhere.


Yeah I thought it may be triggered by a leak, but I just don't see any.

size of the intake piping ? if it's not leak or popped hose (Fuel reg has an irritating habit of popping on ours)..

never heard of this issue even with the bigger piping ..

I had this code with the AGP CAI. I got it to go away by putting the stock box back on. IMO I think it is intake tube size at the MAF that causes this.

^I was told by multiple people that this could be thrown by filling the car while engine is running or by not tightening the gas cap. All of these people are fairly reliable. But Im sure it could be from what you say as well. I didnt get this code till I put on a turbo back exhaust, and have not gotten it again since I placed a defowler on the car.


Nope.. Filling w/engine running will NOT set a p0171. Only a P044X type code, and only under certain conditions.

Member Anubis and I both had this code after AMS intake. Doesn't seem to be causing any problems with knock or temps.

Member Anubis and I both had this code after AMS intake. Doesn't seem to be causing any problems with knock or temps.


yup and still having it :mad:

oh well.......

Anubis, do you have the intake with the extra bung to the solenoids? Because I installed my MBC and closed off that bung, then took the same trip that caused the code before and it stayed off. Not proven by long-term testing yet but something to consider.

Seems like the ams intakes have been having this problem. Has anyone tried to duplicate the exact diameter of the stock intake on the ams intake in the maf sensor area? The larger diameter of the ams piping is going to make the maf think less air is going into the motor and reduce fuel. I would try to modify the ams in the maf area to replicate the stock diameter.

Does this make sense to anyone? Just a though.

Seems like the ams intakes have been having this problem. Has anyone tried to duplicate the exact diameter of the stock intake on the ams intake in the maf sensor area? The larger diameter of the ams piping is going to make the maf think less air is going into the motor and reduce fuel. I would try to modify the ams in the maf area to replicate the stock diameter.

Does this make sense to anyone? Just a though.
Seems to make sense but would restrict airflow?

i threw this code as well. but with 2 others.....it ended up being my MAF sensor.....are you running high idel RPM's? around 2,200? if so it is prob. the MAF sensor. hope this helps.

Seems to make sense but would restrict airflow?

It may restrict airflow a little, but you'd still have the benefit of the larger filter.

Anubis, do you have the intake with the extra bung to the solenoids? Because I installed my MBC and closed off that bung, then took the same trip that caused the code before and it stayed off. Not proven by long-term testing yet but something to consider.

I have the extra bungs on mine.

It is weird though because sometimes it takes almost a week or so for the light to come back on, and other times only a few miles...in other words very inconsistent. This is all while driving the same routes,speeds and outside air temp etc... for the most part.

I also have the AMS IC and UICP and am thinking of getting one of their intakes. I'm sorry for your CEL but would greatly appreciate keeping the this post updated as you get things worked out Anubis and Iconz.
Thanks.

I also have the AMS IC and UICP and am thinking of getting one of their intakes. I'm sorry for your CEL but would greatly appreciate keeping the this post updated as you get things worked out Anubis and Iconz.
Thanks.


Mine is for sale ;)

no in all honesty in AMS's defense members are running this intake with no CEL. Every car is slightly different, and that is car modding life. That being said no updates from me until Cobb comes out with a tune for the AMS intake.

Once this happens I will be the first in line, and say goodbye to my CEL. Otherwise it has consistently come on and gone off for about 1,000 miles now. Sometimes I get 100 miles before it comes on sometimes I get a mile......frustrating to say the least, but I am over it.