Corolla, exhaust rattle

paulginger2

Hi all,
I have posted before with regard to an exhaust rattle, which i thought in the end up was the famous inlet manifold rattle. I know now that it is definitely not that.
On certain revs, 2-3k, i have a loud rattle coming from under the car.
Nearly like a cakkle sound if that makes sense.
I have taken it to my mechanic friend and he inspected the exhaust, nothing is loose shaky about to fall off or anything like that.
So visually it is fine.

What could it be? Is it some of the internal baffles rattling inside the exhaust??
How can i locate which part of the exhaust is making the rattle??

The car is running very well, except for a slightly rough idle in traffic, ranging from 500-750. Going up and down, car shudders likes its gonna die and revs go up again, in that kind of a cycle.

Could this be related to the exhaust? I have already cleaned the throttle body i.e. (Sprayed carb cleaner into it)
I am totally broke so mechanic is out of the question.

Again any help or comments, questions would be appreciated

Thanks

joujoujou

It can be pieces of what your catalytic converter's contents used to be, especially if you ever drove your car on misfire.

Apart from throttle body's cleanup, which actually can be done way better when it's removed off the car, clean idle control valve as well as mass airflow sensor (MAF sensor's cleanup is very easy, tbh).

And reset ECU - disconnect battery for a couple of minutes, or locate EFI fuse (usually in engine compartment) and pull it out for the same amount of time.

paulginger2

Thanks for your reply, im assuming the cat is the most expensive part of an exhaust?

I was gonna take off the throttle body but couldnt get the hoses disconnected from it, so i took the easy option!
I know where the maf sensor is, i cleaned it already. Is the idle control valve located inside the throttle body on the corolla??

Ill disconnect the battery anyway and go with the reset.
Again thanks for you help!

paulginger2

I rang a toyota garage today and got a quote for a replacement catalytic converter.
It comes in at 795 euro which is obviously not gonna happen!
The other pieces are much cheaper but i dont wanna replace them obviously if they are not the problem.

To me the sound, sounds like it is coming from the middle under the car, i assume thats the cat???

If anyone can shed some more light on this i would appreciate it, thanks

JohnBoy26

It could be the front exhaust shield that's rattling. I have seen a few of them that have cracked that caused a rattle like you described. This can also give the illusion that the noise is coming from underneath the car.

paulginger2

How do you mean cracked? Like split?
Visually it looks fine, i can see this from the engine bay yes? Just so im in the right area?
There is no rust on it, its not touching the exhaust, or any other part that i can see.
Its dark now but i will have a proper look 2m

Thanks for replying!
Please keep the responses coming, this has been doing my head in now for a while and im sick of it tbh.
So any and all help appreciated

cletus

If you think it might be coming from the exhaust, put it in the air and tap (read hit😊) each section with a rubber mallet. You should hear the bits knocking around inside if its the baffles breaking down, or cat internals etc.

paulginger2

Ok ill do that, thanks.
It only happens when the engine is up to temp too, so im assuming the exhaust is warm then too

Its much more noticeable going uphill too, a steep hill will make it rattle really loudly

Esel

paulginger2 wrote: »

I rang a toyota garage today and got a quote for a replacement catalytic converter.
It comes in at 795 euro..

If you need a new cat, you will get a spurious one a lot cheaper from the UK. Probably worth checking prices here too - Fastfit etc. and your local motor factors.

cletus

Bear in mind, a lot of spurious cats have a much shorter life span, only a year to 18 months in some cases, may be a false economy if you plan on holding on to the car for a while

paulginger2

Well i plan on driving it till its death tbh,its got 93000miles on it.I would like to get the same again out of it if i could! I got a price of about 60euro for a cat off a scrapyard, maybe if it was in good nick and was cleaned out somehow it might be worthwhile? Also i would assume it would have to be welded in? Or is there some form of joint that can be made to connect the pieces? Like a collar type thing?

I wont be able to get it in the air to bang on it with rubber hammer to check for rattles til next week most prob.

creep

I got a new exhaust box and got it fitted for 110 euro. Shop around.Garage supplied the exhaust box and fitted it for 110. Cc was also fecked and got new one for and fitted for 180

joujoujou

But you're not sure if cat is a reason of your problems.

paulginger2

Thats exactly it, i dont know which part of the exhaust it is, but i will take a chance and say its not the back box, as the sound seems like its coming from the front/middle, underneath. Which could be either middle silencer/ catalytic converter if im right??

joujoujou

Or something else.

JohnBoy26

paulginger2 wrote: »

How do you mean cracked? Like split?
Visually it looks fine, i can see this from the engine bay yes? Just so im in the right area?
There is no rust on it, its not touching the exhaust, or any other part that i can see.
Its dark now but i will have a proper look 2m

Thanks for replying!
Please keep the responses coming, this has been doing my head in now for a while and im sick of it tbh.
So any and all help appreciated

Sorry I meant to say front exhaust bracket instead of shield. It's located behind the engine.