Date:         Tue, 3 Sep 2002 10:28:21 -0700
Reply-To:     Helge Weissig <helgew@GRAJAGAN.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Helge Weissig <helgew@GRAJAGAN.ORG>
Subject:      too much NOX
Content-Type: TEXT/PLAIN; charset=US-ASCII

failed the smog test (CA) with barely too much NO (low rpms only but high
value at high rpms as well). All other measures were good although HC
seemed a little high... got a new cat and after much fiddeling with the
right top screw of the old one got it on ok. Took the van ('86 Westy) for
a drive (about 5 miles) and it seemed to run just fine. Let it sit for a
few minutes and when starting it back up, the engine started right away as
I turned the key (usually she cranks twice, without laboring). When I got
back onto the road, things didn't go that smoothly: very little power, did
not get above 55 mph on the freeway and seemed to loose power with more
gas. Pulled over after about a couple of miles and noticed a very hot cat
with sulfuric smelling smoke coming from engine compartment. I figured
that I might have accidentally wiggled the O2 sensor loose or damaged it
while trying to get it out of the old cat, so I checked the cables and
made sure all was connected. Let the engine/cat cool down and drove home
with no further troubles.

Inspecting the old cat did not reveal what I was hoping for: utter
destruction. There were a few specks of dirt in the porcellain channels
and quite a bit of soot in the intake. Also, the intake porcellain face
was not flat but looked like someone scooped out about an inch of it.

Soo... not sure what was going on, buddy and I measured the O2 sensor's
output as suggested by others on the list. Seemed weirdly erratic and
could not get the engine to react much when connecting the 1.5 V battery.
Finally checked all spark plugs and plug wires since there seemed to be a
spark noise. Found two loose plugs but everything else seemingly in order
(5k Ohm on the wires).  With all plugs firmly screwed in, O2 sensor and
ECU were behaving quite nicely, the former fluctuating between just above
.5 V and 0 V, the latter adjusting the mixture (judging by the rpms at
constant gas) depending on whether the battery was connected or not.

Now my questions:
1) what could have caused the high NO values when the old cat did not
"*look* broken. Obvious answer seems it is actually broken. But why then
would HC and CO not be off the richter too?

2) did I kill the new cat on the first run when it got so hot? I guess I
will find out after the next smog check... :)

3) what, if any, role could the loose spark plugs (some soot but no
extreme noise) have played?

thanks so much for any input!!
h.