tran23

service engine light came on. Computer reads increase emissions. Got the code read p0171 p0174. Bank 1 and 2 are running lean?

Trinity Autosport

Take off your MAF and clean if with MAF cleaner.

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_7070079-P_x_x?cm_mmc=ACQ-_-Google-_-enhancedRM-_-7070079&ci_src=17588969&ci_sku=7070079&ci_gpa=pla& ci_kw={keyword}&gclid=COaN-ojvn7UCFc6DQgodVRoAFw

Stephen Max

This can be caused by a couple of things. An intake leak after the maf sensor will cause a lean afr, but the dme will compensate by adding fuel. The dme is limited to how much fuel trim it will add, however, so if the leak is large enough the CEL will light up with codes related to running lean.

Another possibility is an air leak at the exhaust header, in which case the O2 sensors will detect the unreacted oxygen and send a false lean signal to the dme, which then tries to correct fuel trim in an effort to bring the afr back to stoichiometric by adding fuel, resulting in an overly rich running engine, even though the code says lean.

An air leak at both headers is unlikely, however. Since you have codes for both banks, an intake leak is more likely.

tran23

alright thanks for your input and quick response in gonna try cleaning my maf sensor. If not I work at the BMW stealership and have them look at it

kushane

I had the same codes when one of my ccv hoses sprung a leak. You could take a carb/throttle body cleaner and spray it on intake side hoses (and the ccv hoses) while the engine is running and listen for the revs to rise.

In my case, it was the hose from the ccv to the dipstick tube that had a leak.

tran23

it didn't work now my car doesn't go far couple 100feet then chugs alot

pcy

Try this - disconnect the electrical connector on MAF and start the car. Does it run better?

tran23

I think its either my lower intake boot or my oil separator. M54 have issues with those and the effects are what I'm having

pjinca

I had the same thing, REALLY rough idle, CEL, Increased Emissions (actually had about 4 pages of errors when the mechanic looked at it), the oil separator was cracked in half. Car was never right again which is why I traded it in. I had 2005 530 (M54) after fixing the oil separator it would spew smoke under acceleration on occasion, I now have a 2008 550.

tran23

once I find out the problem I'll fix it. I was planning on selling it soon anyways. About to buy a e30 for $800