2005 525I system too lean and ticking noise
 

I have a 525I the 192HP version i think possibly n54 or n52 b25. I've had a slight ticking noise from the intake area around the engine bay. the ticking noise is subtle, but I can still hear it. my engine light is on but when I read the codes all I got was codes P0171 and P0174, which means system to lean on all cylinders. So, either all my 4 oxygen sensors before and after the cats have gone bad, or I have a vacuum leak or my MAF sensor is bad. but I've checked for vacuum leaks, and can't find anything, those 2 codes are the only ones coming up. What could my ticking noise be? feel free to ask any questions if the text is to bare boned, I'll try to answer the best I can. and yes, this model does have the DISA valve.

Coupule things...

It is probably an N52. The N54 wasn't out yet.

Put the last 7 digits of your VIN in Realoem.com to get your exact build date and model parts list.

The ticking is a design problem with the N52. BMW went through 3 iterations of "fixes" for the issue. It has to do with lack of oil getting to the exhaust hydraulic lifters. First "fix" was to rev the crap out of the engine to refill them with oil. Second "fix" was to replace the exhaust lifters with a new improved part. Third and final fix was to replace the cylinder head with an improved design. I have a 2006 N52 and have the newer exhaust lifters. Engine still ticks some. Never been a problem as far as I can tell.

I think this is the latest bulletin:
https://static.nhtsa.gov/odi/tsbs/20...50095-9999.pdf