z4 service engine soon issue

[Mr.Smithers]

Hey guys, so my 2003 z4 was running great until last week when the check engine light came on and the car rpms started hesitating. I plugged in the code reader and got 7 CODES!!

The codes are:
P0171
P0305
P0313
P0174
P0306
P0304
P0300

4 of the codes are cylinder misfires so maybe coil issues but why would all 4 just come on at the same time? This is really perplexing and I dont know what it could be. If anyone had a similar issue I would love to get their input.

[StickMon]

Did you try clearing them to see which ones come back?
If you haven't scanned it in a while, some could have been "one offs" that didn't set the SES light when they happened.

[Mr.Smithers]

I did try to clear them but all of them came back on again. Could it be the 02 sensor causing all this?

[StickMon]

Hard to say, but I think you're correct that the cylinder misfires are probably not coils, but rather mixture related.
Those are a symptom, not a cause.
It would help if you had a BMW specific scanner, like a Peake Research or DIS.
Do you know what the other 3 codes are claimed to be?
Results will be a little iffy with a general P-code scanner, but a clue none the less.

[Mr.Smithers]

The other 3 codes are as follows:

The P0171 code means that, on the first bank of the engine, the fuel system is running weak or a vacuum leak exists near this side of the engine. A lean condition occurs when the engine either receives too little fuel or too much air.

Code P0174 indicates that there is a lean condition detected by the Engine Control Module (ECM). A lean condition will be created if there is too much air, and not enough fuel, in the air fuel ratio (AFR). The ECM is designed with the capability of adjusting a lean condition back to normal, but only in small to mediocre amounts. If the air fuel ratio requires more compensation to return to normal than the ECU is capable of, code P0174 may set.


P0313 is a generic OBD-II trouble code that is displayed in the powertrain control module (PCM). The code is an indication that the PCM has detected a misfire in one or more of the engine’s cylinders along with a low fuel reading in the fuel tank. The code is set in the PCM only after the engine has completed a minimum of six revolutions after starting, a misfire is detected, and the fuel level is down to the reserve portion of the fuel tank.


And of course the other 4 are cylinder misfires, any idea what can cause all these simultaneously?

[StickMon]

It all points back to running lean. That's what's causing the misfires.
Since I'm an ///M-only amateur expert, at this point I'll have to defer to the 3.0 experts.
Check for obvious vacuum leaks and do a search for "vacuum leak" and "running lean".

Come-on 3.0 guys. What are common causes for running lean?

[Steeler]

Intake boot is a common culprit. Item 3 http://www.realoem.com/bmw/enUS/show...diagId=51_4848
Make sure all vacuum lines plugged into the back of the intake manifold have zero cracks and are fully seated on the outlet ports.