'94 Dodge Spirit- [non brake] vibrations from underneath floorboards

Recently my 1994 V6 Dodge Spirit began making odd vibrations. They varying in intensity, from subwoofer-type vibrations to full out rattling. It definitely happens when the car is idling; I’m not sure if it occurs when the car is moving, too many other noises. They usually seem to come from the floorboards underneath me. It’s not a brake issue–my mechanic was “almost positive” that my old brakes were the cause, but fixing the brakes did not fix the vibrations. Any ideas?

Vibrating, Rattling Brakes At Idle ? Oh, Well.

What about a catalytic converter with the catalyst coming loose or breaking up internally or how about the exhaust heat shields, externally ?


Have the motor & transmission mounts checked.

Thanks. By the way, the noise is a lot louder when the transmission is engaged; when it is in park, it is a lot fainter

I second the theory that you have broken motor and/or transmission mounts.

If these are vibrations you can feel, I “third” the vote to check the motor mounts.

If these are “vibrations” you can only hear, I second CSA’s suggestion to check the heat shield on the cat converter. If it’s loose, it can be secured with a large worm-drive hose clamp from the hardware store. And while you’re under there you can shake everything with your hand and see what other loose parts you can find.

While a rattling converter (loose internals) is unusual, it isn’t impossible. The catalyst is a fancy metal sputtered onto a ceramic honeycomb, and crumbling is possible. To find out, you can try shaking that section of the pipes by hand. If it’s crumbled, you should hear it rattle.

I took my car into a different shop today, and the diagnosis stunned me. There was a gaping hole in the exhaust pipe, and the heat shield was a little loose. By gaping, I mean a 4-6 inch gap that was obvious the moment the car was up on the lift. I’m pretty unhappy with the first shop for totally missing an obvious call, twice, to the tune of two separate brake repairs costing me $430. Fixing the exhaust pipe and heat shield only cost me $26.00 at an exhaust shop. The first repair shop will be getting a polite yet strongly worded letter in the mail from me shortly.

Thanks for posting back and letting us know. It’s sad that you lost money on an incompetant or dishonest shop, but at least the car is fixed now.

I appreciate all the advice. I don’t mind the money spent on the front brakes to some extent, they were due anyways for replacement. But the rear brake repair really irks me