CEL P0171: Bank 1 Too Lean

jersey_emt · Oct 21, 2004

I'm throwing this CEL.

From what I've read, here are some possibilities.

1. Leak in intake tract after MAF (checked and triple checked, can't find any leaks
2. Vacuum leak (checked, gauge shows 20 vac)
3. Dirty/Malfunctioning MAF (how to clean/test?)
4. Bad/sticking EGR valve (how to check?)
5. Fuel pump (doubtful, as I can clear the code, turn the car on and the CEL sometimes comes on after a few minutes of idling
6. Bad front O2 sensor

Other symptoms:
1. Occasional drop in RPMs when idling
2. Spark plugs are due for a change soon (29K miles)

Any thoughts?

jersey_emt · Oct 21, 2004

Car runs perfectly other than idle.

Mods: Injen CAI converted to SRI, Spool hardpipes. Stock boost.

Dexter · Oct 21, 2004

Hmm my friends speed is doing this with Injen CAI and Apex DP, stock boost.

we also dont know wtf it could be, checked MAF, leaks, and we were gonna swap front O2s but never did.

BOOSTR · Oct 21, 2004

Never had a CEL, but I too suffered the occasional RPM drop while at idle. Particularily after a long drive. I changed the sparkplugs and it seems to have gone away. I am running an Apex catless and Injen too.

Change your plugs and see what happens.

Sixmil · Oct 21, 2004

I have the drop in RPMs at idle, sometimes its pretty rough and almost kills the engine and then quickly revs up. Pretty much have had this as far back as I can remember.

-Six

DAWIV said:
Never had a CEL, but I too suffered the occasional RPM drop while at idle. Particularily after a long drive. I changed the sparkplugs and it seems to have gone away. I am running an Apex catless and Injen too.

Change your plugs and see what happens.

changedman · Oct 21, 2004

dont think it could be EGR, i think it'd be the O2....

changedman · Oct 21, 2004

and if your spark plugs were bad, you'd be getting misfire codes, so i doubt its the plugs...

Dexter · Oct 21, 2004

have you tried just resetting the ECU? i think it might have something to do with the injen.

jersey_emt · Oct 21, 2004

Code comes back after resetting ECU

Dexter · Oct 21, 2004

Try putting the stock airbox on?

changedman · Oct 21, 2004

only thing i can think of is the MAF. theres something happening somewhere that more air is being pulled in than normal or something like that. Otherwise the MAF itself. hmm.

changedman · Oct 21, 2004

A code P0171 may mean that one or more of the following has happened:

* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
* There could be a vacuum leak downstream of the MAF sensor.

so the question is, have you cleaned your airfilter lately?
otherwise, you COULD (unlikely) have a clogged fuel filter
also check your PCV valve.

jersey_emt · Oct 21, 2004

Nope haven't cleaned the filter lately....it's also due for cleaning

Aaron · Oct 21, 2004

i went to the dealer for this as well last week

all those Dip s**** did was reset the PCM. hasn't come back yet.

BOOSTR · Oct 21, 2004

Forgot to mention, I also changed the PCV valve when I changed the plugs. That combination seemed to solve the erratic idle. But I never had a CEL like you. Get 4 plugs and a PCV and put them in and clear the PCM. I did not alter the CAI set up though. Good luck in getting it resolved.

akhilleus · Oct 21, 2004

To clean the MAF you can get this air cleaner that is used on electronics and sensitive equipment. Its just a pressurized can of air. that might help.

^tyrant^ · Oct 21, 2004

i have gotten this code many times now, and i have yet to figure out why. i took it to mazda they claim its a bad O2 BUT they didnt replace it. that was the first time mazda looked at it.. I just got my cat back today from mazda agian but this time i had many other problems for them to look at like overboosting to 15 psi, coolant leak etc. ... well the car is still over boosting go figure. well anyway back to the topic they are telling me now that the CEL is from the muffler that i got put on the car, that its leaking. i told them bulls*** i brought the car in once before, when i didnt have the muffler and you told me it was a bad O2 but didnt replace it. so im kinda stuck right now with that, im getting a full catback put on then im taking it back and saying the exhaust leak is fixed, not fix the car right this time.

they did replace some parts
By-pass air control valve and/or gasket
boost control assy
air vlv
boost sensor, R&R

and now my idle is better and stable and im not stalling at redlights

BlkZoomZoom · Oct 21, 2004

What the hell is a boost control ass.?

JerseyEmt- Bring it to the dealer, let them check it out. System too lean codes are nothing to be messed with. Do not try diagnoising a car by asking what fixed other peoples cars, its a bad idea. Also do not just start replacing parts. Diagnoistic procedures are there for a reason, let them use it.

Pay the 1hr. to have the check engine light diag'ed. Then, if its something easy to do, replace the parts the tech. reccomended, if not under warranty.

^tyrant^ · Oct 21, 2004

BlkZoomZoom said:
What the hell is a boost control ass.?

hell if i know, all i know is that didnt fix s*** that was wrong, and i forgot to mention that my belt is coming off the pully and they didnt fix that!@!

and my turbo sounds like ass when its spooling so there is something wrong there but they wont replace it, the gasket on the turbo mani is shot and leaking but they say its not! im just going to keep taking it back to them until they fix it correctly

changedman · Oct 21, 2004

boost control assembly lol

CEL P0171: Bank 1 Too Lean

jersey_emt

Member

jersey_emt

Member

Dexter

BOOSTR

1 OWNR MSP

Sixmil

Member

changedman

changedman

Dexter

jersey_emt

Member

Dexter

changedman

changedman

jersey_emt

Member

Aaron

Member

BOOSTR

1 OWNR MSP

akhilleus

Member

^tyrant^

Member

Attachments

BlkZoomZoom

Member

^tyrant^

Member

changedman

Similar threads

Latest posts