tired hatch

check all your wiring harness connection for anything being unplugged or backwards the only reason i say this is b/c you had the mani off

User 102020

edit: I take that back, according to Interwebs e46s do have an idle control valve.

Niburu

As the owner of 2001 325i here's what i can tell you:
the lean codes can be caused by one or both camshaft position sensors being faulty
also the O2 sensors on the E46 are famous for going bad
pretty much these are the main weak points in the car besides the infamous window regulators

BSeriesTurbo

we've dealt with the cam sensors and all of that on these cars, we see them everyday. This problem seems unique, with nothing pointing in a good direction.

We have an Autologic here that we use for BMW/Mercury Benz, I've taken values of both the pedal input sensors, the throttle valve angle and voltages, and the MAF. I unplugged the MAF this am and the car ran the exact same as with it connected.

Fabrik8

????

You have a MAF problem then. Nothing changed when you unplugged it, no different airflow readings or anything like that?

Did you take those readings with the Autologic when you were driving or just sitting still? You might not see anything at all unless you can get readings during the faulty engine conditions.

The only think I could think that would cause the engine to run the same with the MAF unplugged (other than a MAF or MAF wiring problem) is if the ECU was in failsafe mode and was using fixed values for most of the sensors. That should definitely make itself known though, so I can't think that would be the problem.

BSeriesTurbo

If the MAF was the problem, when I unplugged it the ecu would default to a "basemap" and the problem should have dissapeared. I didn't take readings with it unplugged because I was just trying to see if the problem was remedied or not.

The readings I took were while having a coworker drive the car down the road and recreating the problem.

Fabrik8

So the ECU defaulted to a basemap and threw a fault code when the MAF was unplugged, but the problem with surging was still there?

BSeriesTurbo

Yup, no CEL either, just the code. lol