Trouble Codes: P0305, P0174, P0171

[kbrisson]

A few weeks back, my '06 X3 3.0i service engine light came on. Codes read were P0305, P0174 and P0171. I've read a lot in the forums about possible causes. A few days ago, I reset the codes and they haven't come back, so I am reluctant to spend time taking things apart to look for vacuum leak or other issues I've seen in the forums. Is there some possibility that this was a one-time fluke, perhaps a bad tank of gasoline or something like that? I also thought I read that it could be dirty MAF as a result of oil from a K&N air filter, which I have had one for about a year now.

[AzNMpower32]

Have you noticed any unusual driveability conerns? Unusual sounds or noises?

Usually it takes X times of an error occurance before the SES light illuminates but it does not recur......then leave it.

[kbrisson]

No drivability issues. Light came on at normal highway speed when my parents drove my wife and I to airport, so car was fully loaded, that's it. There is a noise I have noticed for the past several months before, but I cannot determine where it is coming from. Seems like a rotating noise because I can only hear it just as I roll to a stop and the frequency of the "clicking" decreases and eventually stops when I am nearly stopped. I do not hear it when I accelerate from a stop or at normal speeds. I was thinking it is coming from underneath the car, but again the noise is so subtle its hard to tell.

[TerminatorX5]

do some light preventative maintenance - check the air intake hose for cracks, holes, spray MAF cleaner onto the MAF sensor (follow the proper directions), clean the throttle valve from the gunk... all of that will cost you about $10-15 in chemicals from a local parts store and about an hour of your time...

[kbrisson]

Finally got around to checking this out. Turns out there was a fairly small crack in the hose going to the idle air control valve. Ordered replacement from nearby Turner Motorsport ($40) with shipping. Access to the hose clamps is a PITA, even with surrounding components all removed. Since I had new spark plugs awaiting installation, I ended up changing those while everything was apart.