Occasionally (once a month or two?), my 530D performance changes during a journey. There is a noticeable additional lag when you accelerate and also there is a "throaty" exhaust tone from somewhere underneath the car (as if it were blowing from a hole, but I don't think it is?). If I park while it's doing this, there is a distinct rubber smell from under the car. It's done this for the last couple of years (& is today) and it's bugging me!

Any similar experiences out there or ideas?

Thanks.

Ian.

 

Not sure of your model year has a particulate filter in the exhaust, but if it does, this sounds like the periodic cleaning that the car does of the particulate filter. If your exhaust goes straight out at the back you have one, if it curves towards the ground you don't......

 

I've got the filter, so it must be this cleaning process. Any idea how it works???

Thanks.

Ian.

 

I have the same effect in my 530d. I think the way it works is that it needs to raise the temperature of the exhaust gases to burn off the soot that has collected in the particulate filter. I think it does this by injecting additional fuel? Try resetting the average fuel consumption indicator when you start hearing the boomy exhaust and you'll also see that you get a pretty alarmingly high consumption figure during the "boomy" period.

Mine sounds like I have a hole in one of the mufflers but quickly goes away.

Ditto on the weird smell too.

 

I'll try that next time.

Thanks.