[Ndgurl311]

When I accelerate my car from a stop it sounds like there's a rattle coming from the back of the car I have searched everything I even looked at the mufflers to see if something was loose down there but I really can't figure it out

 

[Vipre77]

Is it a metallic noise or more like plastic?

Here's a checklist of things that I'd look for, in order:
1. Bumper cover and any of the trim pieces on the rear doors, rocker panel, wheel wells, bumper, and around the liftgate opening and the license plate (and license plate frame if you have one).

2. Rear spoiler. Someone a while back had posted a service bulletin that Mazda has released for the rear spoiler making noise on some cars, but I don't recall under what circumstances the service bulletin applied. If it turns out that is your problem, then Mazda has a fix for it. I don't know if production cars come with this fix from the factory now or not. Mine was built in Aug. 2015 and does not have it, but it only rattles when I close the liftgate. Not sure if it's bad enough that they need to fix it, but I plan to mention it anyway at my next oil change.

3. Exhaust hangers. Make sure the muffler and exhaust tips aren't swinging around too much and banging into things. They should move a little, but there should be some obvious resistance there when you try. If there's little or no resistance in their movement, they aren't being supported properly.

4. Check the spare tire storage area. Might be something loose and bouncing around in there.

5. If it's none of those things, then get it checked out by the dealer ASAP. It could be any number of other things, ranging from the worst case scenario being something loose in the drivetrain which could be causing damage the longer you put it off, or best case scenario is something simple like a piece of trim you couldn't see or a loose heat shield on the exhaust somewhere. Regardless, if you're still under the factory warranty, any of these possibilities should be covered.

 

[Ndgurl311]

Thank you! It's the muffler tapping my tow bar. They put a piece of rubber on the edge of the muffler that was vibrating on the tow bar. All is good!

 

[jtonline]

2. Rear spoiler. Someone a while back had posted a service bulletin that Mazda has released for the rear spoiler making noise on some cars, but I don't recall under what circumstances the service bulletin applied. If it turns out that is your problem, then Mazda has a fix for it. I don't know if production cars come with this fix from the factory now or not. Mine was built in Aug. 2015 and does not have it, but it only rattles when I close the liftgate. Not sure if it's bad enough that they need to fix it, but I plan to mention it anyway at my next oil change...

When you take your car in, Vipre77, this is the post from Anchorman which includes the TSB: http://www.cx3forum.com/forum/131050-post7.html. The fix is to replace four protectors between the rear spoiler and rear window glass with thicker ones. This gives tension to the rear spoiler and stops the rattle when closing the tailgate.

 

[Vipre77]

When you take your car in, Vipre77, this is the post from Anchorman which includes the TSB: http://www.cx3forum.com/forum/131050-post7.html. The fix is to replace four protectors between the rear spoiler and rear window glass with thicker ones. This gives tension to the rear spoiler and stops the rattle when closing the tailgate.

Thank you, sir!

 

[anchorman]

Thank you! It's the muffler tapping my tow bar. They put a piece of rubber on the edge of the muffler that was vibrating on the tow bar. All is good!

Whenever I read a thread like this, I'm always wary about whether the car has been modified in any way and it often turns out that somebody didn't really check their work very well. Glad you got it sorted although I hope that rubber is a suitable solution for a hot exhaust.

 

[TiGrayMSM]

I wouldn't blame the install so quickly! I have the same vibration due to the towbar. It only happens on hot days after an extended period of driving, when you go over a rather large bump in the road. At first I thought the towbar had moved, but I checked all the bolts and they were all torqued properly. There just is not too much clearance between the bar and the muffler, and the hangers are quite soft (especially when hot). I will try polyurethane hangers I have lying around and see if that helps.