Hey,

A friend of mine at the college has a '93 945 w/Regina which is getting a terrible rattling noise while accelerating, but only while accelerating hard... if you keep it below 3000 RPM it's fine... It's a very loud rattle.... Loud enough to be heard a significant distance from the car. Sounds like a paint can with a few ball bearings in it being shaken on one of those machines at the paint store at high speed. If I had to say it was something, I'd say some type of shroud is loose and vibrating, but I can't find anything of the sort.

The only think I can see wrong with it is that it needs the valve lash adjusted.(new Shims) He reports a puff of black smoke under high RPMs when shifting up or down, but over the last 2 weeks I don't see any oil missing so I think tis' simply running a tad bit rich. Also, the plugs show no signs of oil burning. Exhaust system seems OK... the pipes from the cat back have been replaced recently. The cat itself hasn't, and I've heard catalytic converter elements melt down and cause a rattling noise, but not this loud or crisp. It seems like it may be in the general area of under the car somewhere though... Could it be the CAT or is there some type of U joint up there??? It's worth mentioning that it CANNOT be duplicated while the car is neutral or park, so I don't think it's a rod or a valve...

Any thoughts appreciated!

Yours,
Fred