Buzzing/Trilling noise underneath Car?
Thread Starter
3rd Gear
Joined: Oct 2019
Posts: 3
Likes: 0
From: Atlanta, GA
Buzzing/Trilling noise underneath Car?
Hello All, I’m new here on the forums and have run across an issue with my ‘90 C4. When I’m sitting at idle with the car warmed up, there’s a bizarre buzzing noise that comes from about about halfway back underneath the car, near the passenger side catalytic converter. I had it on a friends lift and couldn’t determine if it was coming from what might be the starter or the transmission casing. The noise goes away as soon as the engine is revved. Any ideas?
Le Mans Master
Joined: Dec 2005
Posts: 8,581
Likes: 967
From: Communist Colorado
I had something very similar... it wound up being the diverter valve on the passenger side exhaust. The diaphragm wore out and would make a weird sound sort of like a Kazoo.... it sounded like it was coming from the cat area but it was the diverter valve. I just drilled mine out to make it stop. Theyre cheap enough though and available if thats what it ends up being for you.
Thread Starter
3rd Gear
Joined: Oct 2019
Posts: 3
Likes: 0
From: Atlanta, GA
I had something very similar... it wound up being the diverter valve on the passenger side exhaust. The diaphragm wore out and would make a weird sound sort of like a Kazoo.... it sounded like it was coming from the cat area but it was the diverter valve. I just drilled mine out to make it stop. Theyre cheap enough though and available if thats what it ends up being for you.
Le Mans Master
Joined: Dec 2005
Posts: 8,581
Likes: 967
From: Communist Colorado
Last edited by 81c3; Apr 6, 2020 at 02:49 PM.
