Rattling Noise in 5th Gear

[mmaclan1]

Rattling Noise on 5th Gear

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I have a 2013 Mazda5 Automatic. I have been struggling to figure out what is causing a slight rattling noise in what seems to be located in the engine. When I accelerate high speeds between 80km - 90km/h. At first I was not able to duplicate the problem, so I tried a couple of things that would hopefully resolve the issue. After looking around on the internet, it advised that air/fuel combustion could be misfiring and to try premium fuel. This did not resolve the issue. It also advised that the fuel injectors could be dirty ad might not be providing adequate fuel in the cylinders. I tried some Gumout All In One, and after this I tried lucas oil upper valve lubricant fuel system cleaner. This did noy resolve the issue.

After more investigation, I was finally able to pin down when the rattling occurs. I switched to manual mode and found that the rattling occurs when I accelerate, between 1750 and 2000 rpm on 5th gear. The rattling goes away, shortly I after it goes above 2000rpm.

Has anyones encountered this issue before? any insight is much appreciated. Thanks

 

[teetee1]

What's the mileage of the car and has the transmission fluid changed according to maintenance schedule? Is there any trouble code from OBD2 connection?

 

[mmaclan1]

The car has 76000km (47200miles). I bought the car at 63000 km, and has had one scheduled maintenance. The scheduled maintenance was only an oil change, and inspection. My assumption would be that they atleast inspected the fluids at 63000km and at 71000km. I will have to double check the maintenance report to see if it has been changed.

I dont have OBD2 reader. Ive been looking to invest in one. Of note though, the check engine light is not on.

 

[negusm]

Is this an actual rattle? Or a vibration you can feel?

If it's just a rattle, that could be a bunch of stuff...often a loose exhaust heat shield that vibrates at exactly a certain RPM range.

If it's a vibration that is rattling...I'm thinking more like in the drive line has an issue. Usually only at idle will injectors cause enough vibration to cause any rattle.

 

[mmaclan1]

Its actually just a rattling sound. when you hear it, sounds like it's coming from the engine. As I have been trying to figure this out and searching the web, the heat shield seems to keep coming up, like you mentioned. That is probably my next step.

 

[negusm]

Yeah, a rattling like that is going to be something that's physically loose. If you're not actually feeling a vibration at those RPMs or the engine isn't hesitating, then there's not much wrong.

Have you tried, in park, revving the car out to 2000 RPM? It's odd if the sound only happens when actually accelerating in 5th gear.

 

[mmaclan1]

UPDATE: So I had taken my Mazda5 for it routine maintenance at 80,000 km. Oil Change, Brake Service, and they also added the Throttle Body Service, as they did not have a record of it being done, and noticed carbon buildup. Surprisingly after this service, I have not heard the rattle ever since. It has been over two months and have done everything I can to get it to rattle again. I believe it's been fixed for me. Hope this helps anyone having a similar issue.

Additionally, it was not the heat shield that I had suspected. The dealer inspected it and it was just fine.