Troubleshooting: System too lean Bank 1 and Bank 2. Last option

[wesTCU540i]

I keep getting system too lean CEL errors.
I'm about to take the car into the shop because I cant figure this out.
I cleaned the MAF really good, took apart my intake to look for leaks, didnt see any, cleaned it, cleaned the filter. Made sure the gas cap was all the way clicked down. The system too lean message is comming from bay 1 and 2. It could be o2 sensors but its unlikely because the car has 60k miles 2001 540i. Plus, the chance both o2 sensors are lit up at the same time is not very likely they would of both gone out at the same time..
The shop Im considering taking it to said they can find out whats up for 45 bucks, like seeing if the maf is shot, the o2 sensors are shot, intake leak. I figure its better to pay 45 bucks to figure it out rather than start replacing parts for $100s that dont need replacement.

Any other suggestions for things I should look at before I take it in?

[nicegsxr]

How does your car run though? And about your o2 sensors not gone yet at 60k, you are nearing the end though. Have you changed out your fuel filter? Running lean is risky for btw.

And if your indy can pinpoint your exact problems for $45 then go for it, but alot of times they cant pinpoint it for you. My friend's car has been in his indy for over a month now with similar problems on his 323ci. They told him the same thing when he first brought it in that they can pinpoint the problem.

[wesTCU540i]

Car runs good. But I dont really have much to compare it to, Ive never driven anyone elses 540 and when I bought it from the lady who sold it, the next day this light came on and she told me that it was just because the gas cap wasnt on very good, implied it might need a better gas cap. The reason she told me that is I assume she had seen this light before and taken it in and thats what the bmw dealership had told her and never investigated the matter any further..

For all I know it could just be needing another gas cap, but I doubt that would send off these codes in both banks and plus, the gas cap seems fine to me and is on there as tight as possible..

So I really dont have anything to compare to as far as how the car runs. It runs good though Ive taken it to 130 without any sort of hestitation and I can accelerate plenty fast. Idle seems steady.

I havent replaced the fuel filter or pre cat o2 sensors. I guess I'll just let the indy check it out and see if he can tell me what it is before I go buying $100 dollar parts. I just had wanted to solve this problem by myself but I dont think its going to be that easy.

[slig5440]

Car Idles Rough But Is Ok On Road.1st Code Was P1189--changed Out
Dirty Air Filter.new Code Is P 1188.no Visible Leaks.these Show Fuel
Control Bank1 Sensor 1 And Bank2 Sensor 1.also Received Several
Cylinder Misfires And P0170 Fuel Trim Bank1.have 130 000 Miles And Never Replaced O2 Sensors Or Fuel Filter--plugs Look Clean--bought
Car At 100 000 Miles.could Fuel Filter Cause This Problem And Still
Run Great At High Highway Speeds. Thk For Any Help

[nicegsxr]

P0171 - System to Lean (Bank 1/2) :

* Fuel system
* Excessive fuel pressure.
* Leaking/contaminated fuel injectors.
* Leaking fuel pressure regulator.
* Low fuel pressure or running out of fuel.
* Vapor recovery system.
* Induction system:
: : - Air leaks after the MAF.
: : - Vacuum Leaks.
: : - PCV system.
: : - Improperly seated engine oil dipstick.
* EGR system:
: : - Leaking gasket.
: : - Stuck EGR valve.
: : - Leaking diaphragm or EVR.
* Base Engine: :
: : - Oil overfill.
: : - Cam timing.
: : - Cylinder compression.
: : - Exhaust leaks before or near the HO2Ss.

These are all the diagnostic for this code from Ford.

I would definitely check all Vacuum hoses first when something like this happens, I just asked about the fuel filter because I notice you were mentioning o2 sensors and I just thought of fuel filters and bad fuel. If its not any intake leaks or vacuum hoses, then I would change out pre-cat O2 sensors at your miles anyways and they arent that expensive each.

[wesTCU540i]

Think it would be better to pay the indy mechanic $45 bucks to diagonose it...
Or change pre cat 02 sensors before I take it to the indy mechanic? And see if that fixes it?

Wouldnt an indy mechanic be able to tell if the o2 sensors are shot by doing some sort of voltage test or computer reading?

[nicegsxr]

Car Idles Rough But Is Ok On Road.1st Code Was P1189--changed Out
Dirty Air Filter.new Code Is P 1188.no Visible Leaks.these Show Fuel
Control Bank1 Sensor 1 And Bank2 Sensor 1.also Received Several
Cylinder Misfires And P0170 Fuel Trim Bank1.have 130 000 Miles And Never Replaced O2 Sensors Or Fuel Filter--plugs Look Clean--bought
Car At 100 000 Miles.could Fuel Filter Cause This Problem And Still
Run Great At High Highway Speeds. Thk For Any Help

I would start with pre-cat 02 sensors for your miles especially when you never had them changed out. P1188 is Fuel Control (Bank 1 Sensor 1).

[nicegsxr]

Think it would be better to pay the indy mechanic $45 bucks to diagonose it...
Or change pre cat 02 sensors before I take it to the indy mechanic? And see if that fixes it?

Wouldnt an indy mechanic be able to tell if the o2 sensors are shot by doing some sort of voltage test or computer reading?

The only real way to test O2 sensors would be on a flow bench with calibrated gas mixtures or by comparing the signal between a used and known good sensor on a running engine with an oscilloscope.

Here is a link to how to test o2 sensors on your own.
http://www.wps.com/LPG/o2sensor.html

At Sparkplugs.com your pre cats o2 are $93.85 a piece.

[wesTCU540i]

Thanks alot nicegsxr! That site you linked gave me alot of information on this problem.

[slig5440]

thks for the info---i will try the pre cat sensors--i just coudnt understand
why i didnt get a oxygen sensor fault

[bimmerfixr]

thks for the info---i will try the pre cat sensors--i just coudnt understand
why i didnt get a oxygen sensor fault

Probably not O2 sensors. Do you know anyone with a 540 or 740 that you could swap the MAF with?

[slig5440]

Will Try To Find Someone To Help

[nicegsxr]

Probably not O2 sensors. Do you know anyone with a 540 or 740 that you could swap the MAF with?

I also second the suggestion on MAF sensor, but at his mileage I would swap out the O2sensor eitherway because a O2sensors and MAF sensor are known to not throw any codes until its completely dead on BMWs.

When the O2 sensor fails, the computer runs in open loop mode and the fuel mixture to the engine will not be correct. This can cause the engine to ping, run rich or lean, and/or miss.

[racermp]

stealershipo.....

[Hotswimmer]

Here's something to look into - it's what was causing the fuel trim problem I had: http://forums.bimmerforums.com/forum...d.php?t=641517

[civilator]

we had a similar problem with the same error and it was a broken exhaust pipe going into the exhaust manifold.

[killcrap]

check fuel delievery pressure.

[x2nervisx]

sorry to bring up an old thread but any updates on this? I also have my ses light on and its telling me that bank 1 is running lean.

[Hotswimmer]

That can be a number of things, though the fact that it's only one bank limits it a little more. Leaking intake manifold gasket is a common one. So is bad O2 sensor. What was the actual code - is it lean at idle or off-idle? How is the car running?

[stevo328]

if i had to say i bet your intake needs to be resealed and the crank case vent valve replaced. we see it all the time. even more than faulty maf sesnors. It is one of those things that is dif to diag but it you have mechanical knowledge pretty easy repair just time consuming. The parts are cheap also.

[kory2000pr]

if i had to say i bet your intake needs to be resealed and the crank case vent valve replaced. we see it all the time. even more than faulty maf sesnors. It is one of those things that is dif to diag but it you have mechanical knowledge pretty easy repair just time consuming. The parts are cheap also.

That was my first impression Crankcase ventilation system leaking.very common.If you have to replace the cranckcase vent make sure you get all the vaccum hoses and the rear seal.

[x2nervisx]

the car runs great right now. I cleaned out the maf with maf cleaner and I haven't cleared the ses codes to see if that helped at all. I'll look in to the CCV. Is it hard to replace on the 540?

[jcommare]

I think there's a kit that has a bunch of various hoses along with the CCV valve...I just had mine done...do not have a heated garage and it was 5 this am...

jc

[x2nervisx]

well i checked the codes again today and it's bank 1 and 2 running lean. Still suspect the CCV?

[chamana]

i had these two codes 170 an 173. Today i checked th hoses and the grommet for the ICv to make sure there were no air leaks. I assumed it wasnt an o2 sensor as the codes kind of indicate an issue for 2 sensors and i though " what are the odds both are screwed atthe same time"

I bough the car a few months ago and so i thought "Whay Spark plugs are in there"

Turns out they had "champion" plugs. Changed them to Bosch and so far havent gotten the check engine light yet. I'm going to take it on the highway in a few minutes and put some load on the system.