My 2004 545i has been having a rough idle for a while now. It is MOST noticeable when the tranny is in DRIVE, the Air Conditioner is on, and the car is NOT moving (ex. a red traffic light or stop sign).

I have also noticed that when driving very very slowly (0-7 mph)there is a pulsation feeling in the drivetrain. It feels like the engine is spitting out little spurts of power because of the rough idle.


One morning, when I parked in the parking garage, I noticed a weird noise from under the hood...a pulsating noise. I kept the engine in Drive and pulled the emergency brake so I could get out to inspect.

The noise was coming from the MAF compartment. You can hear it in the video below. This loud suction noise only happens when the Air Conditioner is on.



I unplugged the MAF Sensor. It took a few starts to get her to start up, but the air intake is perfectly smooth now (no loud sporatic suction noises). The rough idle is gone and the pulsating feeling when driving very slow is also gone. The car drives like a dream with the MAF unplugged. However, with the sensor unplugged, I got the Check Engine Light, a slight engine stall when accelerating, and bad fuel economy (about 16mpg compared to 19mpg).

I went to BMW today (even though my warranty is expired) and asked for the shop foreman to have a look. Unfortunately he was at the doctor today. The service manager questioned me because he has no idea how the engine would even run with the sensor unplugged.

My warranty is expired but the MAF was replaced about 6 months ago. I should have a 2-year warranty period for any part that was replaced. However, the Service Manager told me that the MAF has to show BAD before they can replace it.

I brought this car in a month ago for a rough idle. They replaced the spark plugs and performed a fuel injector flush. It didn't fix it but did make it better for a little while. They "goodwilled" the spark plug change but I had to pay $165 for the fuel injector flush.

Since the original problem was not resolved, I should not have to pay for the labor for them to test the MAF sensor since they should've checked all of that when I originally brought it in under warranty.

Any thoughts about the unplugged MAF sensor eliminating those issues would be great!!

 

that is weird that your car ran well with the maf unplugged.

have you ever cleaned the throttle body on your car?
did you try a maf cleaner spray to see if that would improve things?

 

I didn't try anything yet. Before i try a cleaner, I've read that the MAF Self-Cleaning relay is a common problem so I'm going to check that next. I hope the relay is bad...that would probably solve my issues. That may be the reason the MAF had to be replaced the first time...now this one is acting funny. If the relay seems good, my next step is to clean it with the cleaner.

I'll post the results.

 

Hi, I know this was years ago but, how did you get on with the MAF unplugged? I've been having the same issues and now, with the MAF unplugged, it runs great! But, is it safe to do this, up until I take delivery of the new MAF sensor I just bought. Ok, should have tried cleaning the old one first but...!

Did you get this issue sorted and, how?

Any advice you can give would be much appreciated...

 

If you dive you car without the MAF you will only see your MPGs go down. I would of tried to clean it and see what you got. You will be fine in whatever you choose to do. But clean it and see if it corrects your issue.