Originally Posted by madman
Would be interesting to hear results of this.
Do you have a description of how you did it?
My car has nearly spent as much time in the stealers as it has with me so i'd rather look at something simple like that myself.
Quite easy really, just needs a bit of patience and some tools (2 different torx bits, a socket, sorry, can't remember exact sizes) plus some electrical contact cleaner. I bought some stuff from halfords for £3.99. Most important that it's spray stuff that doesn't leave residue.
In the attached pic, you need to remove 3 torx screws, 2 from the front of the air inlet and one from the top inline with the BMW badge, then just ease this moulding off the main airbox unit, I think the pipe is roughly triangular in shape with no clips or brackets.
Next you have to remove the airbox by undoing the 2 bolts on top of the box and the jubliee clip that holds the outlet pipe in place. Be careful as there's a rubber bung on the bottom of the airbox (5 in the diagram) that can fall away into the engine compartment as you remove the airbox.
Once the box is free, carefully turn it over as the MAF cable is still attached. You'll see 5 or 6 torx screws which all need undoing to separate the two halves of the airbox. The two halves are a snug fit so they will need some gentle force to separate.
Once the box is open, you'll see the air filter. It should be cylindrical with the paper cone covered by a felt type cover. Mine was black but the paper part of the filter was clean. Pull off the filter and you should see a tube screwed to the housing with a section hanging down - this is the MAF sensor. You can either try and disconnect the MAF sensor cable or treat the sensor with the cable in place. I did this but placed some towels underneath the housing.
With the housing ready with towels underneath, I sprayed the MAF sensor (inside item 7 on the diagram) with the contact cleaner spray. I did this a few times from different angles then left it for a couple of mins so the excess dripped away and most of the spray evaporated. I then wiped the housing clean, but never touch the sensor with anything as it's very easily damaged.
Once cleaned up, it's a simple case of putting it all back together.
Drove it yesterday and I noticed some difference in pickup. It certainly didn't feel as sluggish and the auto box seemed to know what it was doing rather than snatching at gears. But the acid test was with my wife driving it today. Unprompted she commented on how much more responsive the car felt and also smoother picking up speed. She normally doesn't notice things like this so I'm taking it as more than my imagination. Still too early to comment on fuel economy but it's got a full tank of fuel and everything is reset. We'll just have to see how it goes.
As a note of caution, I have read that this can be a temporary fix. When a sensor is on it's way out, cleaning it get's it back to normal for a while but if it's knackered, it will pick up crap again and give out duff readings. New non duff sensors are probably less susceptible to picking up dirt etc.
I also wouldn't take any crap from the dealers. They profess to their kit being able to identify faulty MAF sensors but there are plenty of cases that this is simply not true. Changing the sensor for a new one has made problems go away all together.