It doesnt happen when im in park with the car running. Only when Im idling in drive. Once I get going it goes away. Im 98% sure its the cat. I checked the heat shield, and thats bolted, and sturdy. If i turn the car off, and bang the cat I can hear some stuff rattling inside. I wouldnt mind changing the cat, because thats probably the problem. I just want to know why it only happend when idling in drive. My car idles in park @ about 800 rpm, and it idles in drive @ about 400 rpm. if that helps thanks.

 

Thats odd. It's very plausable that the stuff inside is rattling around, but it's weird that its only in drive. You're sure it's not the sheild right? Both sides are held down nicely?

 

definitely - the heat shield is not the cause

 

mine rattled when the ends of the tail pipes where hitting on the frame after one got bent abit so it might be that

 

Mine just started doing this too, a Catco converter that's a year old now. I suppose idling in gear has the engine under load enough to vibrate the exhaust just right to rattle it. I'd guess the cat. bed is loose inside. Myself, I'm wondering whether to try to get it replaced or live with it, sure don't like it though.

 

have you checked the air tubes that go into the cat?

if the tubes sag just a little they will rest on the cat and make a hell of a clanky noise

i know from personal experience from having two dual cat cars

if that is the case just bend the bar off the cat and see if that was your prob

good luck

 

Ok...So i double checked everything, and checked the things like you guys recommended. The air tube is not hitting anything, and the heat shield in the front and the back is secure.....Im going to go ahead and change the cat...

I figure I might as well go with the high flow cat since im going to change it. I measured the inlet and outlet diameters with a caliper gauge, and the inlet tube(coming from the y pipe from headers) is like 2.992...im figuring its 3 inches. The outlet size shows the same thing. which should i go with?? I need one that has a flange on the outlet side, and slip on the inlet. with an overall of about 21 inches.
Catco Direct Fit Catalytic Converters: CTO-9118 - summitracing.com
This one from cummit seems like it would fit best,
eBay Motors: 3.00" 3" Catco High Flow Catalytic Cat Converter (item 8072385309 end time Nov-01-06 18:29:33 PST)
and this one on ebay is a lot better price...will either one work.. The one from ebay says its 14 inches long...am i going to have trouble??

Thanks.

 

It would be very easy and very helpful to simply remove the heat shield and see if that fixes your problem before you go out and spend a pretty penny IMHO

 

As the above post mentions. I have checked the heat shield - and that is not the issue..

 

The direct fit will have the outlet flange, easy install. The Ebay one looks like a universal fit, will have to do some cutting and fitting, maybe get an adapter or weld to the existing pipe. Also, the front slip fit on the old cat can be really tough to get it split and off the car. Helps to have a torch or larger cutoff wheel to cut the pipe extension on the front of the cat and then split the pipe stub.

 

thanks tom
thats what i needed to know

 

so was that it?