Contour Enthusiasts Group Archives Forums General Troubleshooting How can i prove that my cat is bad?

Also, my '95 Contour also had the rattle you described (at 2000-2500 rpm), even after replacing the factory recalled cat on it. And it turned out to be coming from a heat shield that is mounted above the cat, on the floorboard (that keeps the cat's heat from getting through to the doghouse/ firewall/ floorpan area. I just made a simple aux. support bracket to hold it better, and now the rattle is gone.

Wouldn't a loose heat shield rattle all the time and not just when the car is first started. This sound does go away after the car starts warming up. I am not sure if it is the cat either....

Aren't car problems fun???? hehehe

:p

When the shield would rattle during cold, it was loose, but when it would heat up and get hot, it would bend and warp from the heat, and get tight in the mounts, and rattle would be gone. If you seen the chinzey holddowns for the heat shield, you'd understand how It could probably rattle

I had both a loose heat sheild and broken ceramic matrix inside the cat.

if your cat is really plugged, your engine will actually start pinging. Mine started with the common pinging culprits like leaky injector seals/buildup in upper and lower IM. Then I started having CEL, so my guess is the pinging caused the engine to run really rich which caused my cats to meltdown. Anyhow I digress, with the cats plugged your top end should feal really slugish. With mine I still had a LOT of intake noise though, so it sounded like it was going fast but really wasn't. I ended up just bringing mine to a dealer and they gutted the cats for me, after that all was better.

BTW sorry for the long post

IIRC you can test for a clogged cat with a vacuum gauge. Hook it to a source of manifold vacuum and rev the engine to 4K rpms or so and if the vacuum drops off (after initial stabilization at 4K rpms) then you've got a restriction in the exhaust system.

Karl