Catalytic Converter issues

I own a 1997 Mercury Tracer, 2.0L, with 158k miles. I'm posting here because it's the exact same vechile as an escort and no one is posting in the Tracer forum :)

For about a year now my Check Engine light has been on for a bad catalytic converter. My state doesn't have emissions checks and a friend told me it isn't that important right at the moment to replace it (the mechanic I went to was trying to rip me off by purchasing the CA emissions passing cat for over $700!).

But I'm wondering if it is now time to replace my Cat. Over the past few months my vehicle has started to randomly stall as I decelerate under 15MPH. Sometimes it will fully stall, but it would restart no problem. When it happens now I tend to pop it in neutral quickly and the engine goes to a normal idle speed with no issues.

My mileage also seems to be suffering pretty badly, as I'm getting around 23MPG.

I don't appear to be having any acceleration problems, as I've read here as a common issue for a bad cat.

I plan on purchasing a perfect fit cat online for about $150 and an automotive store agreed to install it for $102. They wanted to charge $249 for their cat.

Do you think these problems may be my cat and it is worth spending $250 to fix it? I don't have the means or the tools to install it myself, unfortunately :)

Do you know the exact code? Available code reading/scanning at AutoZone for free.

The exact code will help a lot but I suggest you replace the oygen sensor. This would account for the poor mileage. Usually when a cat goes bad you will have poor acceleration or no symptoms at all. I really don't know of a code that would specifically identify the cat as being bad.

I never thought about the code...the mechanic just said the check engine light is on due to a bad cat. I'll swing by an Auto Zone and get the exact code and post it.

You can check the cat with a vacuum gauge. A reading of 16 inches or less at idle indicates a restricted cat.

Ditto on the oxygen sensor.

It is easy to replace and can be done yourself. Costs about $30-50 though.

I'd bet the cat is just fine.

So maybe the mechanic was just trying to rip me off by saying my cat was bad when it was really just my o2 sensor. How would I know which one to replace? I'm pretty sure my model has more than one...at least that's what another mechanic told me in 2001 when I had one replaced...if I recall...he said I had 3 or 4?

There is no calibrating or anything like that involved? Just take out the old one and place in the new one?

No calibrating. Replace the one that is in the cat.

You may very well have a cat problem though... but I would suspect the sensor first.

As mentioned above, find out what the code is before you do anything.

I went to AutoZone and my car has the following error codes:

P1744
TCC - Excessive Slip Detected During Full TCC Engagement"

P1443
EVAP System Vent Control Function Problem

P0420
Catalyst System Efficiency Below Threshold (Bank 1)

I'd focus on the EVAP concern first. It has to do with the vacuum sweep of the gas tank vapours ... including the gas cap, the carbon canister, a valve and a sensor ... and several feet of hoses. I'd make a thorough inspection/replacement of hoses "first-thing" ... you can bet there are breaks in the hoses. Also make sure the passageway into the throttle body is not clogged-up ... this is where the hose system starts, and sometimes gets stuck up ... a needle should clear it.

After clearing the EVAP code, work on the exhaust sensor problem. Remember that bank #1 is against the firewall on a sideways Vee engine .. but bank #1 is all you have on a sideways 4 cyl. I've had to replace the sensor prior to the cat on my D's '97 Escort ... used a Bosch replacement ... works OK, but the info that comes with the sensor is a bit lacking.

I'd focus on the EVAP concern first. It has to do with the vacuum sweep of the gas tank vapours ... including the gas cap, the carbon canister, a valve and a sensor ... and several feet of hoses. I'd make a thorough inspection/replacement of hoses "first-thing" ... you can bet there are breaks in the hoses. Also make sure the passageway into the throttle body is not clogged-up ... this is where the hose system starts, and sometimes gets stuck up ... a needle should clear it.

After clearing the EVAP code, work on the exhaust sensor problem. Remember that bank #1 is against the firewall on a sideways Vee engine .. but bank #1 is all you have on a sideways 4 cyl. I've had to replace the sensor prior to the cat on my D's '97 Escort ... used a Bosch replacement ... works OK, but the info that comes with the sensor is a bit lacking.

THanks for all the info!

I have no idea where to find all of what you are talking about with the EVAP system and I think that's a little out of my league, so I'll have to take it to a shop for that. That probably has a large impact on my mileage, no?

For the exhaust issue, by exhuast sensor do you mean the O2 sensor (http://www.autozone.com/servlet/UiBroker/?UseCase=C001&UserAction=answerRequiredQuestion&Parameters=%7C%7ESensor+located+before+catalytic+c onverter&PageSync=4)before the cat? I figure with a little looking and possibly some help on locating the sensor's location I could replace that (providing I don't have to remove anything to get to it. I don't really have much in the way of tools).

If you have enough tools to remove the battery and air filter, you will be able to inspect most of the hoses going to and from the carbon canister (mounted below) ... you will probably find hoses with holes ... easy to replace!

If you can reach the Oxygen sensor from below, an adjustable wrench may work.

Thankfully I found a friend with a workshop and was able to replace my CAT. I definitely found out my cat was bad when exhaust started coming out of my engine compartment :) No more exhaust comes from my engine, which is good, and none of the old codes have appeared after a week.

But now I have two new codes:
P0443 and P0444.

I've started a new thread on this here (http://www.automotiveforums.com/vbulletin/showthread.php?t=681559)