[net.auto] The stench of an overworked catalyst

dsi@unccvax.UUCP (Dataspan Inc) (12/26/85)

> My '82 Celica has this wicked rotten-egg smell as the engine is warming up.
> It only seems to happen on days that it snows, other (cold) days the smell
> is there but it's not so pungent.  Obvious choice was the catalytic
> converter, so I dumped some C.C. cleaner in it.  That didn't seem to help
> it.
> 

     I thought only old Buicks smelled like rotten eggs.  Your catalyst is
working great, unfortunately for your nose.  There are three causes to the
el-stinko problem:

     1) (assuming it is carbureted)
        The vacuum break in the carburetor (it's a little vacuum motor which
holds the choke partially open once the engine gets running) is misadjusted
binding or broken.  Since it is a vacuum motor, the possibility of a torn
rubber part is not unreasonable.  Similarly, anything which makes the engine
run unbelieveably rich will result in impressive odors.  Some cars have air
injection downstream of the LOC (lightoff catalyst), a malfunction here can
cause excessive odors and underbody temperatures. "Tune-Up In A Can" won't
work here (or anywhere); the only solution is to check the obvious stuff
(filters and so on) and then bench the carb and test it using the manufacturers
set up procedures....AFTER you inspect the emissions control system to make
sure all the little hoses are going to all the correct vacuum motors, solenoids,
vacuum resistors, check valves, and so on.  Every hose should be reasonably
soft and free from cracks and leaking. Many vacuum breaks and enrichment
valves are connected to so much other junk that a leak in a place halfway
across the car will pull the vacuum break or other devices off spec.

        (assuming it is fuel injected)
        I'm not familiar with the EFI system used in Toyotas.  The car may
default to the "rich" side of the map if the oxygen sensor fails.  Air
injection difficulties also apply here. Some EFI equipped cars have a cold
enrichment device which require adjustment.

     2) Fuel
        Disgusting, sulphurey smells can be caused by refiners who ignore
ASTM/API methods for verifying the sulphur content of gasolines. Try a few
tanks of real gas if you think the stuff at the local Hop-In or Seven-Eleven
is more akin to industrial waste.  Smell the gas you are purchasing (don't
get down and sniff at the nozzle, but try to get a whiff of the lighter 
vapours).  Heavy mercaptan (sulphur) content is obvious because the gas
will smell patently awful.

     3) Ignition timing. Yes, Ignition timing.  My parents had said aforementioned
Buicks which stank to high heavens, and (reportedly) a resetting of the
ignition timing resulted in more palatable smells. I can't verify this,
though. Check it anyway, using the manufactuer's procedures (particularly
true for EFI equipped cars).  If the distributor behaves in any weird way,
have it serviced at a competent distributor shop.

     Dealers will be notoriously unsympathetic to these causes, and it will
be rather expensive to have them investigate all of 'em.  Since nasty
cold startup smells are common complaints, though, the Toyota dealer may
have some service bulletins on them.

-dya-