Catalyser question (auto, fuel, best, exhaust)

[Jaggy001]

The catalyzer in my daughter's car was loose. So we took it to a reputable muffler shop where we live and had it replaced. Worked fine for a couple of weeks and then the check engine light came on again. My daughter took the car to a different shop who said that the catalyzer was bad and the O2 converter was probably bad too.

So, here is my question .......

It is my understanding that the catalyzer is a "non working" piece of equipment in that all you do is pass exhaust gasses over it and it converts them into non-poisionous gas. That suggests that something else is not working, possibly the O2 converter.

The muffler shop where we had the work done has told us to bring the car in so they can have a look at it. But I would like to go in reasonably smart. Consequently, I would welcome any suggestions or ideas as to what might be wrong, what to say to the shop and any other ideas on the best way to proceed.

[trlhiker]

What the heck is a catalyzer? Do you mean Catalytic converter? First of all, make sure you get the term right. The catalytic converter rarely goes bad. Did the first shop actually replace it or just repair it? Sounds like your O2 sensor, not convertor, may be bad.

[Jaggy001]

Originally Posted by trlhiker

What the heck is a catalyzer? Do you mean Catalytic converter? First of all, make sure you get the term right. The catalytic converter rarely goes bad. Did the first shop actually replace it or just repair it? Sounds like your O2 sensor, not convertor, may be bad.

The first shop replaced it.

That is my though too that the o2 sensor is bad.

[mikeyyc]

A catalytic converter shouldn't go bad for at least 100K miles, unless you're using leaded gas.

I'd say bad o2 sensor or PCV check valve.

[Mac_Muz]

The cat is a series of honey comb like holes in a ceramic body with in a case, a part of the exhaust. Hot gases flow thru it heating it up, which burns off hydro carbons, and lowers so called toxic emissions.

The O2 sensor is a lamda sond device that nasa developed to create varriable voltage off wasted O2. The device didn't meet the voltage specs nasa needed so the device was put in the market. Boshce took it up for the 0.5 volt the device can create, and used it to lean the fuel mix on most modern injection systems, Other compaines took it up as re-vamped Bosh injection which most cars these days are, in one or another versions of either old or new Bosche systems.

I would highly doubt a 2nd cat is dead almost no matter what happens in a short two weeks.

Not knowing the year make and model makes it impossible for anyone to help you. I might know the system inside out, and upside down, and I might not. I have no clue what vehical yer tawkin' about!

'IF' the 2nd cat is dead too there is a major flaw elsewhere in the injection system, which would almost be so bad the car can't start muchless be driven!

A flaw so bad that the O2 sensor is rendered useless even if it is working. A condition where fuel mix, which is in terms of 14 parts air to 1 part fuel, is much more parts fuel.

In time a long time a cat can sort of wear out, which mostly means gets clogged up with so much crud carbon, that no gasses can continue to flow thru the device.

When this happens the pipes ahead of the cat become red hot in bright sun shine. Not good.

At that point the car may run, and not have power. Out the tail pipe you may hear hissing, as exhaust flow tries to escape thru what ever openings are left in the cat.

One way to show you sort of how a cat works is to hold a candle under a old cooking pot, you no longer care for. The candle will blacken the pot bottom pretty quickly.

Then with a common propane plumbers torch paint with the flame and watch the carbon turn red hot and burn away. That is more or less how a cat works. It has no moving parts.

Maybe another better example might be run a oil lamp with no chimney under a steel window screen, and soot the screen up to be solidly blocked. Then with the plumbers torch heat the carbon away.

Carbon is a bi-product of combustion and can become a fuel.

However in a cat carbon is no longer a fuel and as the O2 is very low in waste gasses, it takes a hotter heat to burn the carbon off. The cat is designed to be very hot, even after the engine is off for a while.

IMO neither the cat or the O2 sensor are the fault, they are the symptoms. Some other sensor is the fault, or a faulty injector could be the fault. This could be a bad MAF, or MAP intake throttle body control, but i can't say what since I have no idea what car it is. There are many sensors, some measure coolant temp, other ambient ait temp, and others.

I may never know since I am a x tech and dated. When I got out there was D Jet, L jet, K Jet and LH jetronic boshe systems, and these were all split year versions, meaning many changes occured with in a single years time. And the buyers of the world paid for experiments.

For all I know, this is some odd American set up with a carb body that sprays 2 big injectors into the intake manifold like a carb did once. So this is the best I can do, atleast for now.

A good auto tech today, is indeed a rocket scientist, just very under paid.

I get the feeling your shop is a Midas, or something like one, which is a bunch of glorified parts changers. They can guess their way sometimes thru a problem, or at least so long as you have money in the bank.