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Mercury Sable Cat. Converter is bad

I have a 2001 Mercury Sable with 114k miles. Just bought it and it ran fine for the most part until one day while coming home from work. It was still running but lost a lot of power and wouldn’t go fast at all. I took it to my mechanic and he told me that this car has 3 converters on the exhaust system. First of all, I think having 3 is over kill and secondly, I am wondering why these things are so expensive. The one up front that mounts to my manifold is $350 just for the part. The one in the back can be bypassed (legally) but why did they make this system so complex and what are my options at this point? If I found a Sable that was being parted out, could I use the converters from that? Would it have to be the same year?

I too think having three is overkill. Send your letters of thanks to the EPA.

They’re so expensive because the material that is the catalyst is a very expensive material.

Since I know nothing absolutely about the Sable that is being parted out, I couldn’t even guess.

So, I’m dyin’ to know, what did the mechanic say was wrong and what did he say needed to be done? Enquiring minds want to know.

If you have three cats, then do you have a v6? That is the only reason I see for 3 cats. Two of them, one one each exhaust manifold are called warm up cats. The are put right up to the manifold, sometimes even built into the manifold so that they heat up and begin working within a few seconds of start up.

The downstream cat is a three way cat and will clean up other emissions like nitrous oxides (NOX). I have seen the leading edge of warmup cats, also known as pre-cats melt and clog the cat. I don’t know why they do it, they just do.

If the cats fit from the other sable, then you can use them.

Whoever told you that the rear catalytic converter can be removed LEGALLY is either lying to you, or they don’t know what they’re talking about.

Tester

The cats in the exhaust manifold are the primary cats and are the only ones monitored. They’re in the manifold to help them reach a higher temperature faster. Platinum Palladium doesn’t begin its magic until it reaches about 400F, and its effectivity is directly related to its temperature. The third converter is aft of the Y-pipe and unmonitored.

Platinum-palladium (an alloy) has a melting point of some 3,000 F. The combustion tempeatures of a cylinder can reach some 3,500F maximum under load and in its hottest spot at the top of the power stroke, however the surfaces are kept cool by the cooling fluid, the temperature drops as the piston moves down, and since the temperature that the exhaust manifold reaches is constantly cyling, it generally will not get hotter than about 1000 degrees or so. A melted converter core suggests a problem.

True about the other Sable. My answer was predicated upon knowing onthing about the other Sable.

I agree with Tester…You are NOT allowed to modify/remove ANY OEM emissions equipment.

I too agree with Tester. Now that I’m officially stating that, allow me to suggest…

the same mountainbike: He is saying that something is off with the engine. Could be a coil or plug or something. So the part for just one of the cats is a lot of cash. I hope this will take care of the issue.

I’m not convinced that you’ve been given a proper diagnosis. How did your mechanic determine this lack of power is related to converters and that all of them are bad? This sounds more like a WAG to me and I’m having a hard time seeing the car running fine one minute and like garbage the next due to a clogged cat.

A clog in the converters or anywhere in the exhaust can be easily revealed with the use of a vacuum gauge; assuming the engine has no ignition miss, etc.

A weak fuel pump can also cause a problem like this but that is also a guess at this point as not enough is known about the car or how any diagnosis was done to really know what’s going on with it.

He told me that he took the cats off and used some kind of camera that he has to look inside to see what kind os shape they’re in. He indicated that 2 were bad and that the engine is what could be causing the problem.

What has probably happened is the pre-cats have come apart internally and sent all that debris down the exhaust plugging up the main cat. This will cause the engine to lose power because of the restricted main cat.

This can happen with any pre/main cat system.

Tester

Actually, Steve, what I said was that for the cat converter core to melt (or for the ceramic core to collapse) there needs to be something wrong with the engine,

There may ultimately be something wrong with the engine. But to suggest that I’d need to see whether the converters were the cause of the power loss AND if so, exactly why. I don;t have enough hands-on knowledge to guess, so I’m going to go with your guy’s guess…however I would like to know exactly what he saw. Clogging with black carbon would suggest a serious metering problem or serious oil burning. A collapsed honeycomb would suggest unburned fuel entering the converters…there’re a number of possible causes for that.

Perhaps the best approach at this point is for you to measure those boneyard converters and if they’ll fit try 'em. I won;t comment on the potential legal consequences of the boneyard guy selling you the converters.

"Just bought it and it ran fine for the most part until one day while coming home from work. It was still running but lost a lot of power and wouldn’t go fast at all. "

That’s not a reason to buy expensive exhaust system parts…Did the CEL come on?? Has an exhaust system back-pressure test been performed?

I think you are barking up the wrong tree…

If this guy is going to all of the trouble to remove cats, examine them with a Bore Scope, and if something had really come apart inside of the cats then why did he not just shake the debris out before reinstalling them?

It would be much simpler and easier to throw a vacuum gauge on it and determine if there’s an exhaust restriction or not. That should not take more than 30-60 seconds of his life and the car doesn’t even have to be raised to do it.

I’m still not convinced the cats are the problem either and going from running fine one minute to not so fine the next doesn’t sound like a converter problem to me. JMHO and I could be wrong.