You know how sometimes your vehicle just doesn't feel quite right, but you
can't really point to anything that's a problem? I've been having that
uncomfortable feeling for a while, and I just got to wondering how a person
can check the catalytic converter. I had a truck that I bought because it
wouldn't run, and a replacement of the catalytic did the trick. Do they
slowly become stuffed with garbage and slowly deteriorate the car's
performance, or does it just suddenly happen? I have a 1977 350ci. Most
everything is new, but I haven't done anything to the exhaust yet.
I've never had a "stuffed" catalyc converter..(although I've heard of this
being a problem) I can tell you though,
that I had a broken baffle in a muffler and after replacing the muffler..
the car ran way WAY better.
A '77? I'd say it's a decent chance the converter is plugging..
Back in those days many people would run leaded gas in them
and that would melt the honeycomb...
Has the gas filler area been knocked out to fit a leaded nozzle?
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errrr..... you are absolutely right they were filled with pellets,
and the pellets would melt together with the leaded gas.
Not honeycomb. I forgot about the plug on the bottom
we would remove to dump out the pellets... LOLOL
do a pressure test, you can make a adaptor out of an old O2 sensor to
connect to your fuel pressure gauge with a short length of hose, if it
is more than 4-5 inches it is plugged up, you can test to see if it is
working by using a infrared temp gun, check the temps before and after
the cat, should be at least 100 degrees hotter after the converter.
some times the substrate will come loose and you can hit the converter
with your hand and hear it rattle around (make sure that puppy is
cooled off, they get real hot)
On Wed, 5 Oct 2005 18:06:50 -0700, "BDragon"
As far as using the o2 sensor, all you are trying to do is hook up a
pressure gauge upstream of the converter to see what the back pressure
is. snap-on sells a cheap adaptor that screws into the o2 sensor bung
and you just hook up a fuel pressure gauge to the adaptor and watch it
as you raise the rpm of the motor. you will know pretty quick if it is
plugged or not. this is about the only way that most shops check for
the temp method tells you if it is "lighting off" or not. so I guess
that really is not a issue here.
as far as modifying a o2 sensor you can just take the guts out of it
so all you have left is the part that screws into the o2 sensor bung
and weld or glue a nipple onto it to connect your hose to your
as far as other methods of checking temps, I am sure there are, but
every one I know does it with a infrared gun now, and that is really
not a good test for it being plugged. Greg
On Fri, 7 Oct 2005 18:12:50 -0700, "BDragon"
Plus you could always do the old fashioned way by unhooking it...
hehehe, I like the O2 Pep Boys style adapter and pressure gauge
but how often would you ever use those later??? arrgh... nuttin ever
easy or cheep.... :-)
Now I think, but not sure on this.....
1) They will look for anything that is different than stock, excluding
parts with CARB Numbers.
2) They will put it on the sniffer to see if it passes...
So as far as I understand (which might be wrong) if they see 2 CATS and
came with one you would fail, even if the car passes the sniffer.
I'd think the ONLY important thing would be passing the sniffer no matter
what parts were on the car. Now-a-days a person could build 500hp and pass
any state emission tests. I don't see the harm. But I'm not a
As far as California is concerned, Ric's got it right -- it's
bureaucratic and political. The California Bureau of Automotive Repair
(BAR) goes by a Bible that for other than mass produced models is error
prone. We (me and the BAR) used to play the every-other-year smog game
with my gray market 911, bought in Europe. It always passed the sniffer
but had a distributor that wasn't on the list of approved items. The car
would fail visual inspection at the local smog guy and I'd go the 40
mile drive to the "referee station" (a private contractor that answers
to no one). They would issue a notice of failure. I would mail that to
Porsche America in Reno. Porsche would return a form letter that my
distributor was an "authorized substitute."
Back to the BAR referee station with the Prosche letter. They would pass
the car. Two years later it was back through the same process. The prior
correspondence didn't count because the manuals hadn't been revised to
include my distributor. Etc. Etc. Etc.
Finally, I got smart and took the critter to a Prosche dealer for smog.
California law let the dealer sign off on the distributor, OK the
car and pass it. $ 105 bucks for a smog inspection at the dealer was
cheaper than $ 45 at the corner smog guy...figure.
These people look at the VUN. For a given VIN there's a configuration
list of things they look for. If I had taken my European 911 and
upgraded it with all California approved components it would have failed.
I have seen inspection options on the smog testing machines that provide
for two CATs but don't know what that might mean. I fear that getting
the two banks into the ball park might be tougher than the average of
the two -- maybe an ECM averaging two O2 sensors??? Next time someone
goes for smog it might be a good deal to ask and post the answer here.
Actually it's getting more complex than that. My 04 had 2 pre-cats and 2
cats with a pre burn and an after burn o2 sensor for each side. The computer
is reading the exhaust input and then its output to make fuel trim settings.
What one state says will mean nothing to another states set of laws, most of
all Kalifornicate. The federal laws state that it must be as it came from
the factory, any modification to the exhaust configuration is a no no. Even
the add on split after the muffler is not legal but not enforced by states
that don't have mandatory exhaust compliance testing.
The only out I've seen is the age of an old car making it exempt and that is
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