[V8] Clogged Cats? - '90 V8q

[Kent McLean]

robert.a.dupree at jpmchase.com wrote:
> Description:
> a.  car starts up from cold perfectly
> b.  warms up fast in water-temp, faster than I've ever seen
> c.  exhaust flow at the tip seems minimal air, but super-hot.
> d.  car is drivable - but a bit sluggish
> e.  after 10-15mins of steady cruise car bucks, tach drops to zero, will 
> maintain some drivability with held throttle poz.
> f.  a few miles after 1st buck event car dies & won't restart until cool.
> g.  when cool all is fine by cycle is repeatable.

I'm no expert, but I don't think a clogged cat would get more clogged 
when heated. Yes, there is some expansion of the material, but the
degradation of the honey-comb is (or should be) what is causing the 
assumed clog.

How is the heat under the hood when this happens?  My 2 cents would be 
on the RMP sensor or crank position sensor, one of those twins that 
slowly dies due to old age and heat. See:
http://www.audifans.com/twiki/bin/view/Audi/NoStartV8
http://www.audifans.com/twiki/bin/view/Audi/RPMSensorNOSTART

-- 
Kent McLean
'94 100 S Avant, "Moody"
'89 200 TQ, "Bad Puppy" up in smoke