2003 BMW 330 runs briefly and dies


I have a 2003 BMW 330xi. Near 200K miles on it.
Last week I unhooked the main air filter from the car (including the electrical cord that connects to it) and this included also removing the whole case for the air filter. I was doing this to see if I could find a possible leak of fluid of some kind (thought it was ATF fluid but now I’m not sure).
Anyway, put everything back and now the car won’t work right. I can start, but it will run for a second or two and then stop. I called my mechanic who said it was probably the imoblizer. I tried many things to reset and fix that (unhooking the negative lead on the battery for a while, locking and unlocking the car in various forms, pulling fuses to reset the system and replacing the key fob battery) all which did not work.
So I am in need of some help. I can’t tow the car anywhere and where I live there are few people who work on these cars so I pretty much need to fix it myself. Thanks for any help!!

Here’s something that might help:

https://www.2carpros.com/articles/how-to-reset-a-security-system If that doesn’t work you can probably find help on a BMW specific forum.

The immobilzer can be set off by a dozen different causes. The only way to find out is with a scan tool. You might have to bite the bullet. I assume you did check fuses.

The wire you removed from the air box was the air flow meter, if it’s not in right the engine will stall and misfire, if you unplug it and leave it out the engine management will use a default setting and it should run fairly well. The other thing that usually happens Is when the air box is removed it splits the rubber hose that goes to the throttle housing, there’s the large diameter hose but also a small ( an inch or so) that t’s off to the idle valve.

It is not the immobilizer. If the immobilizer is triggered, the car won’t fire at all. In fact. it won’t even crank.

I like Darron’s suggestion of a torn rubber boot, but I would expect the car to run, regardless of how big the leak. Perhaps not well, but I would expect it to run.

If the car shuts off almost immediately after you release the key, I would be looking at the fuel pump, or more specifically, at the power to the fuel pump. Fuel pumps on e46s often fail before 200k miles (I replaced both mine) but remember that the fuel pump spins up and pressurizes the system when you turn the key to On, but then stops and won’t restart until the ECU gets a signal from the crank position sensor that the engine is running. That keeps the car from pumping out fuel after a wreck. Snap up the back seat and pull the cover off the fuel pump (passenger side). Take a couple of sharp pins and put a voltmeter or test light across the fuel pump power wires and see if the power goes off BEFORE the engine dies. You will have to experiment because the power wires look just like the fuel gauge wires. If it is getting power, you can power the fuel pump from a 12 V sources and pump fuel to a jar to visually inspect for pressure and flow rate.

By the way, it is likely that your power steering hoses leak. Old BMW power steering hoses ALWAYS leak a little. However, if you have a massive oil leak, it is most likely the gasket between the oil filter housing and the engine block. The gasket is cheap, it is not too hard to replace, though you have to remove the belts and the alternator. This car is overdue for that gasket if it has not yet been replaced.


Thanks, everyone for the responses! I greatly appreciate it!
I wanted to let you all know what I’ve done since first posting this…
I ended up buying a new MAF sensor piece (the part that connects to the airflow container itself for like 50 bucks at a junkyard). I plugged in the wire and the same thing…the car died shortly after starting it. However, I have since unplugged it completely and the car runs fine now. Maybe even better than before if I am not mistaken as it seems to be shifting better.
I have not driven it far with this unplugged (at most like 30 miles) but interesting that it works without it plugged in. Tells me that the cord may be out of line a bit or loose…haven’t looked yet
Thanks again!

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you could have had a new one for $20 more (A1 Auto). Who knows what condition the used one is. Could have been exposed to the elements for a long time and that wouldn’t be good.

Before doing this, everything worked ?

And now it doesn’t work ?

I’m guessing you missed a vacuum line or other connection.