I got my car back from the body shop. Drove it to work, no problem. On the way home I got a low oil level warning, no problem, I keep a couple of quarts in my garage for just such an occasion. As I got closer to home my car starting idling so rough that the whole car was shaking. Then as I got on my block I got the dreaded "Engine Malfunction" message in my iDrive.
I changed the oil, cleaned and recharged the air filter and added fuel system cleaner. It ran smoother, but still rough idle. It even stalled on me at a red light, probably because RPMs are jumping from 900-200 (normally it runs between 600-700).
I had it checked with a scanner it says either an O2 sensor or the Secondary Air Pump. Not sure what to do, it's running too rough to trust it driving. I have had to brake with my left foot just so I can keep the RPMs up at least at 700.
Funny thing is this is intermittent, it does run smooth sometimes and it smooths out under throttle.
Any ideas would be appreciated.

 

Probably your O2 sensor, if you do have the fault. But also look to the MAF. Oiled filters apparently like to kind of mess with that sensor as it is pretty sensitive

 

Yeah, I gotta figure out which O2 sensor is bad first. I cleaned the MAF really well last night with (member) Toyota2BMW, it didn't help. Now it says "Increased Emissions" but no codes are being thrown.

 

If you were throwing codes before you cleaned the MAF and not throwing them with a clean one, change it with a known working one and see if it makes any difference. Then at least you will know if its the MAF or not. Do you have any friends with the same engine? Might save you some $ before you go out and buy one and it turns out not to be worn.

 

That would be a good idea, but unfortunately just about everyone I know has a 545, 550, 528, M5, or at best a 06-07 530, I have an 05 530 with the M54 engine. D'OH!!!!!

 

I know how you feel. 04 530i here. When you do figure out what it is though let me know. If it is the MAF I might be a bit more reluctant in buying my new K&N filter.

 

You have a vaccum leak somewhere bro or perhaps your DISA is broken or clogged. Just track it down and fix it. It's quite simple with the M54 motor. I own 3 of them....very easy to work on