97 318is N44 running WAY lean?

[Russ in VA]

I had a chance to strap my 318is to a dynojet the other day. It only made 110hp at the rear wheels, which is not that surprising, BUT the concerning part is that it runs WAY lean. Through the pull the air fuel ratio swings from just below 16:1 at the richest to well over 18:1 (off the chart actually). I checked all my boots and vacuum lines but did not find any leaks. We unplugged the mass air flow sensor, did another pull and the readings were about the same. I'm thinking I probably have a bad mass air flow sensor, but I am a bit surprised that unplugging it did not put the system into some sort of default limp home mode that would make it go rich. Any input or good threads anyone can reffer me to? In the mean time, I've sourced a used MAF for a $100 and it's on the way .... but buying a used one does not guarrantee that it will be good either. Input please. BTW, I posted this on 318ti.org and got nothing but worthless sugestions like run some fuel injection snake oil through the car to fix it, please don't bother replying unless you have a technical response. Thanks!

[Jeron]

The last dyno event I went to all the BMW's were lean. I cant remember what the ratio was and I dont have my chart at hand.

So, if I were you, I'd do some searching on the a/f ratios of BMW's on dynojets.

[Russ in VA]

Well, 16:1 and leaner is dangerous on any car, but if you want some objective data, check out the 4th post in this thread:http://www.318ti.org/forum/showthread.php?t=14225&highlight=fuel+injector

[Jeron]

Sorry I didnt read your whole post until now. But my point was that make sure there is a problem before going further. If could be that dyno AF measurement is inaccurate and if there are no other indications of a problem you could be wasting your time.

Here are some discussions you might like or hate...
http://forums.bimmerforums.com/forum/showthread.php?t=595637
http://forums.stangnet.com/showthread.php?referrerid=98350&t=628192
http://www.modularpowerhouse.com/forums/showthread.php?t=1767

[Russ in VA]

Those are interesting discussions, but bottom line, based on the dynojet a/f readings I belive my car is lean. We'll see if the replacement MAF fixes it. The fuel filter is 15k old so I doubt that's it, but I'll be replacing it too. As far as other problems, the car makes less than 100 lbs ft of torque. Lean mixtures result in a loss of torque so that's another indicator. The car seems to lack some spunk, but I don't really have anything to compare it to since I've never driven another m44 powered car and I've only owned this one a few weeks. I need to have my codes read, I had not noticed it previously, but my check engine light does not work (does not come on at start up). I'll be replacing the bulb and see if it comes on. Thanks for the references. I'll post up with further results.