RE: engine resonance/noise

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

... actually it isn't an internal weld, for some crazy reason thre is a very
small weld at one end of the cat that holds it in place.  If that weld
breaks the heat shield is allowed to move around a bit around the cat
proper, and resonate at particular RPMs around 3K or above.  I've seen it
several times on type 44s.  Since I don't have a welding rig I fixed mine by
attaching a wide hose clamp of sufficient diameter around the foreward end
of the cat between the mounting flange and the conical inlet.  This wedges
the front of the heat shield against this conical section and holds it in
place.  I've done this fix on at least 3 cars so far.  My brother-in-law was
amazed that I could ID the problem so quickly and fix it.  He thought he was
in for a new cat too ...

Of course your problem may be one of the other things I and others have
listed, but I do hope that yours is something simple ...

Cheers!
Steve Buchholz
San Jose, CA (USA)

> -----Original Message-----
> 
> 
> Steven
> I do have a catalytic converter - same as in the US, I just 
> hadn't thought
> of an internal weld braking loose..?
> 
> The noise sounds like induction noise actually just much 
> louder.   The cat
> "blockage"? could also be a possible cause for the apparent 
> stumble off the
> line i.e. backpressure caused?  If this is it why does it 
> start at 3000 RPM
> almost precisely??? Is it boost related - running ~ 16 psi 
> with S knobben.