Noise from the rear. Exhaust? Muffler? I am not sure.

[katana85]

Hi guys. I own a 2010 model with 170,000 km. Couple of months now I am noticing that there is noise coming from the rear of the car. What I have noticed so far:-

1 - The noise do change when I am shifting gears. And disappear when I am at 80 km/h. I checked the gear with a specialist and there is nothing wrong. And according to him it could be the exhaust.

2 - Fuel economy is bad and on the highway it used to be 25% of the fuel tank for 150 km. Right now it takes about 50%. Not always, but randomly.

3 - I changed all the fluids in the car. So nothing is old.

4 - I noticed that one spark plug is covered in oil. The mechanic told me there is nothing to worry about and the spark plug gasket need to be changed. Could be not related but I though of mentioning it.

5 - I am assuming it could be the muffler (I did change it 4 or 5 year ago). Dose it go bad normally after these years? What about the catalytic converter? do noise come from them? the spare parts shop advice me to put some liquid to clean the catalytic converter since it is a cheaper option than buying new ones (three).

6 - I checked for leaks but there is nothing wrong also OBD2 scan.

7 - I checked with another mechanic for Exhaust, but according to him there is nothing wrong. No Holes or issues.

Any ideas what can be the issue? At lest what to check since right now since I am lost.


Thanks,

[Brian R.]

Have you recently greased the fittings on both driveshafts? Tire pressure?
The oil fouled plug is not a good sign. It may be the cause of your bad fuel economy. Change it and see if it reoccurs. If it stays oil-fouled, find out the problem.
Check your parking brake to make sure it has some play in it.