gserep1

HI,
I have a rattling noise only upon deceleration when the engine is slightly revved. If I didn't know better, it sounds like an old heat riser on very old cars. I am sure we don't have that on the GS. It only rattles when it is warm.
I blip the throttle up to 3,000 rpms and quickly release it. The rattle occurs around 1800 rpm going down. It is very perplexing. My GS400 has never acted like this before.

I drove 500 miles yesterday, and when I got to my destination, I noticed that I got that rattle for the first time ever. This morning it did not rattle cold at all. I first thought it was in my valvetrain.(rockers, shim buckets and the like, but my exhaust seems really throaty when it is hot, like something is blown out. It seems like a catalytic converter for sure. The only problem is, my performance is not affected, and the cat is not plugged up. I'll check tonight to see if either cat is glowing red when it gets hot. That would indicate a plugged cat. I don't expect to see that since it runs so good.

Has anyone purchased the entire factory catalytic converter assembly from the headers back? How much was it? Is there any aftermarket system out there that performs as well as the stock assembly without excessive noise?

Thanks

jcat_350

check your heat shields and clamps on the exhaust system. they are likely rusted out and hanging off. I had the same rattle for a while and nailed it to a clamp that had rusted and broken.

gserep1

Thanks,
I will check that out. I have never had a problem with the exhaust system, so this may just be the problem.

I appreciate your help.

BCP43002

If your cats were bad you would throw either a 0430 or 0420 code.