'96 LHS cats

I have a 96 Chrys LHS. Its catalytic converters are 3, one for each
exhaust manifold/bank and one central behind those.

The rear/central has been replaced with an aftermarket replacement about a
year and a half ago. The two front ones are 'weird' in their
configuration and there isn't any aftermarket version available in the
sources I've checked. Currently the information obtained from a dealer by
a mechanic friend of mine indicated that -1- the dealer didn't have
any/either in stock and he would have to 'dig them up' somewhere if
necessary and -2- the cost of the two totaled about $1300 retail, with one
of them priced almost $200 more than the other. They look about the same
to simple inspection.

If I should come to need one or both of those cats, how does the common
man solve such a problem?

I've heard that once upon a time there was such a thing as removing a cat
and having it rebuilt with certified cat biscuits/interiors. What is the
story on that?

 

I would have thought that the third unit that you speak of is just a
combiner and not another cat unit, but I see that indeed the combiner
(that takes the left and right-side exhaust manifolds and combines them
into a single pipe that runs to the back of the car) is acually also a
cat converter.

I have no idea why that combiner unit also needs to be a cat convertor.
My '00 300m (with the same engine as your '96 LHS) does not have a cat
converter in that position. Oh well.

Last year I had to replace that combiner unit (with an aftermarkt
stainless steel unit) and one of the flexible couplings on the driver's
side manifold pipes (this on a '00 300m). The combiner unit (in my
case) is really just another muffler (2-inputs, one output).

I've been told that the catalytic convertor units (left and right) are
very expensive. Are you sure that your's is defective? It's relatively
common for the flexible joints to go bad, and (as in my case) it is
possible to replace them without touching the convertors.

How about this:

http://tinyurl.com/cup7re

also:

http://www.streetperformance.com/pa...exhaust/catalytic-converter/868506-50205.html

also:

http://tinyurl.com/cfda6r

I'm surprised that these are mostly listed for under $200 each.

I would think that as long as you can obtain one cat (or two, if you
need both) and not necessarily a unit that is specific to either
Chrysler or to the LHS, that if you find a competent custom exhaust shop
that they can fabricate the pipes and weld the cat units into place.

I'm pretty sure that you probably have stainless steel pipes and
components (at least originally from the factory) but given the car's
age, you probably don't expect to keep the car for more than another 5
years, so replacing any pipes with stainless steel (instead of
aluminized steel) is probably not useful from a cost/benefit POV.

Even if you obtain any of these parts yourself, you should have no
problems handing them over to your exhaust shop for installation.
Although, if you're located in California, things might get tricky for
you.

As I've not yet ever had to deal with a cat replacement, I've never
heard of such a thing, but others here might have.

My gut feeling is that as long as your exhaust shop can obtain a generic
cat (with the correctly inlet and outlet pipe-opening size) that you
should be able to weld the replacement cat's into place with a minimal
amount of modification / replacement of the existing pipes and
(especially) the front coupler.

If the coupler is still good, you don't want to mess with it because
you'll be looking at an extra $100 just to replace it if it can't be
taken apart without dammaging it.

 

MoPar Man wrote:

Thanks for your input.

It passed CA smog check 1 year ago. Recently the check engine light came
on which 'suggested' the R cat's function. A friend with some experience
had a computer that allowed us/him (I was confused by the dynamic readout)
to look at the upstream and downstream O2 levels comparing one side to the
other. If people like to think of cats as getting 'tired', I suppose that
was the idea he was trying to get across. He turned off the check engine
light and I'm waiting to see if it comes back on now.

Good point.

The sources an exhaust welder friend checked for me were for parts about
CA aftermarket jobs he does.

A wonderful term '49 state' (everywhere but CA) appeared in two of those
links.

I understand the 'tricky' concept.

Thanks again. I just got my CA registration renewal for this car and it
doesn't require smogcheck this year, so I'm good for at least June 2010
minimum.

 

If you're not to far away, come to visit a neighboring state,
(NV, AZ, OR), rent a box at one of the shipping & mailboxes stores
(eg UPS Store), go home and order a CC and have it shipped to the box.
If they won't ship via credit card to a non-home address, use mail
order and pay with a money order. Track the shipment online, once it's
delivered, go back and pick up the CC, and close the box. Install.
Problem solved. $$$ saved.

 

Indeed. I grew up in TX, I have family there, and in fact the car was
originally a family member's TX car.

So, I could 'work it out' with getting parts to TX and thence to CA and
solve that 'tricky' part. The tricky part about the installation I'll ask
a few questions next week to see what those guys are comfortable with.

 

.... but all of that is a far-fetched plan B for the future if 2010 Jun has
me with the car and a smog problem.

Plan A is currently doing nothing and wondering if that check engine light
alert is even going to come back on.

I'm thinking that if the same engine didn't even have a 3rd cat, with my
brand new rear cat taking care of a little weakness in one of the front
cats, I'll probably be OK anyway.

 

You sure about that - they're both 3.5L, but I don't think they're the
same design. I could be wrong.

 

Even if they're different, why should the '96 3.5L require a third cat
in addition to the left and right side cat's ?

Also, are there any sensors in the exhaust stream? If so, where?
Before, or after, the cats ?

 

There are sensors before and after both L & R cats. Then later comes the
middle/rear cat.

The before L&R cat sensors are best seen/found from the engine compartment
not far past the manifolds, the after L&R cats from underneath not far
forward of the mid/rear cat.

I had occasion to see all of those sensor connxns Friday.

 

Its much more probable that what is getting "tired" is either the
upstream or downstream O2 sensor that is then giving false erroneous
readings to the engine management system. Either that or another engine
management problem like a leaky injector causing an excessively low O2
reading on one bank but not the other, or an intake leak causing a high
O2 reading on one bank but not the other. Those upstream cats very
rarely fail on LH cars, unless there's a catastrophic problem like a
badly leaking fuel injector or an un-treated misfire that causes a
severe overheat.

 

Not if the front cats are reduction catalysts and the rear cat is the
oxidation catalyst.... if so then all 3 need to work. I'm not sure how
the 96 LH is set up in that regard.

But you're still HEAVILY speculating. Cats rarely fail, CELs are almost
always set by some other problem throwing the O2 readings out of balance.

 

Ah, so. Perhaps it needs more accurate diagnostics than he was using.
Those O2 levels upstream and downstream were all over the map on both
sides to my untrained eye.

 

This is 3 days later and I'm still waiting for the light to come back on.

 

Mike,

If it does, make sure it isn't just the O2 sensor... A much simpler and
cheaper fix.

Bob

 

the rear cat is the reduction cat, the post cat o2 sensors are always behind
the ox cat.

 

If you do replace O2 sensors, do *not* use Bosch sensors - they do not
work on the LH cars.