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daves87rs

Possible Cat Issue?

62 posts in this topic

I've noticed in the last few weeks my wagon has started losing power on its pick up.

It struggles to get up to speed-but seems to be ok once it gets there-until I have stop again.

I was planning to replace the pcv valve, fuel filter-possibly the IAC.

But I've noticed that it really gotten worse as it has finally warmed up.

But I'm wondering- could the cat be causing most of these issues?

(After BV's Fire' and my dad bringing it up-it got me thinking)

The car has hadsome bad gas in it's life-even had some a few months ago (thanks, BP. :censored: )

And the Cat has never been replaced, which is now over 140,000 miles.

What do you guys think?

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What car are we dealing with I'm unfamilier with what you drive. If it is newer with OBD2 with the oxygen sensor after the cat. then it might set a code if your converter was on its way out. Loosing power is a symtom but other times when it plugs up you will experience a rough idle and bad gas mileage. When they get plugged sometimes you can look at the cat and it will show visual distotions in color if it is heating up due to being clogged. Otherwise it might just be time for plugs wires and the regular stuff.

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On my second car the 1992 Oldsmobile Toronado I am having the same issues. It is a project car I am bringing back. It sounds horrible at idle when you start it. Something is open. Once the parts heat up and expand it sounds fine. I am getting a bad gas mileage. I can tell you the wires and plugs have been replaced. The pcv valve is fine because it passed emissions inspection. Also I looked underneath near the catalytic converter the other day I saw the extension pipe moving( vibrating) when it had the bad idle at start up. I also felt heat at my feet when standing by the side of the car. Also when I drive and I hit a rough spot on the street, I hear rumbling like something is loose.

I knew then something was going on underneath near or on the catalytic converter. My neighbor was in my driveway last Friday and we were starting my car, and I had to get a new battery( another story) he said you have a bad cat. I can tell you just by the sound when it starts and that heat. Once you replace your cat, that noise will go away and your mileage will go back up. I can tell how bad it is based on my Ninety Eight. I drove my Ninety Eight on the same streets and it use little or no gas. I drove the Toronado on the same streets and it used gas like it was a GMC or Chevy truck. I had even used fuel engine cleaner from my mechanic.

Here is what a bad catalytic converter will do:

There are two ways a converter can fail:

* It can become clogged.

* It can become poisoned.

There really is no "inspection port" for the consumer or mechanic to see an actual clog in a converter. Often, the only way to tell if a catalytic converter is malfunctioning (plugged) is to remove it and check the change in engine performance. When a clogged converter is suspected, some mechanics temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a change in performance.

A catalytic converter relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter. Leaded gasoline and the over-use of certain fuel additives can shorten the life of a catalytic converter.

A catalytic converter can also fail because of:

* Bad exhaust valves on the engine

* Fouled plugs causing unburned fuel to overheat the converter

Sometimes you can tell that a converter is clogged because you don't go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter. A partially clogged converter often acts like an engine governor, limiting the actual RPMs to a fast idle. A totally clogged converter causes the engine to quit after a few minutes because of all the increased exhaust back pressure.

The catalytic converter, like the rest of the emissions system, typically has a warranty length that exceeds the term of the warranty for the rest of a typical U.S. automobile.

Here is a safety reminder: Do not park your car over tall grass or piles of dry leaves. Your car's perfectly running catalytic converter gets very hot…enough to start fires! You can keep it running well by keeping the ignition system in top shape, to prevent any unburnt fuel from entering the catalytic converter.

The link I got this from:

http://auto.howstuffworks.com/question482.htm

Edited by NINETY EIGHT REGENCY
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What car are we dealing with I'm unfamilier with what you drive. If it is newer with OBD2 with the oxygen sensor after the cat. then it might set a code if your converter was on its way out. Loosing power is a symtom but other times when it plugs up you will experience a rough idle and bad gas mileage. When they get plugged sometimes you can look at the cat and it will show visual distotions in color if it is heating up due to being clogged. Otherwise it might just be time for plugs wires and the regular stuff.

93 Cavalier Wagon w/ the 3.1. 140,000 miles

And I get both a rough idle and bad gas milage. So a clogged Cat can cause rough idle? Like shaking bad?

I checked to see if it turns red and such-but no luck. Though the car doesn't drive that far anywhere at the moment,

so that might not help me...

It got plugs and wires at about 125k, though it was a few years ago....

I was think IAC valve, but now I'm wondering....

The cat has been on the car since new.

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On my second car the 1992 Oldsmobile Toronado I am having the same issues. It is a project car I am bringing back. It sounds horrible at idle when you start it. Something is open. Once the parts heat up and expand it sounds fine. I am getting a bad gas mileage. I can tell you the wires and plugs have been replaced. The pcv valve is fine because it passed emissions inspection. Also I looked underneath near the catalytic converter the other day I saw the extension pipe moving( vibrating) when it had the bad idle at start up. I also felt heat at my feet when standing by the side of the car. Also when I drive and I hit a rough spot on the street, I hear rumbling like something is loose.

I knew then something was going on underneath near or on the catalytic converter. My neighbor was in my driveway last Friday and we were starting my car, and I had to get a new battery( another story) he said you have a bad cat. I can tell you just by the sound when it starts and that heat. Once you replace your cat, that noise will go away and your mileage will go back up. I can tell how bad it is based on my Ninety Eight. I drove my Ninety Eight on the same streets and it use little or no gas. I drove the Toronado on the same streets and it used gas like it was a GMC or Chevy truck. I had even used fuel engine cleaner from my mechanic.

Here is what a bad catalytic converter will do:

There are two ways a converter can fail:

* It can become clogged.

* It can become poisoned.

There really is no "inspection port" for the consumer or mechanic to see an actual clog in a converter. Often, the only way to tell if a catalytic converter is malfunctioning (plugged) is to remove it and check the change in engine performance. When a clogged converter is suspected, some mechanics temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a change in performance.

A catalytic converter relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter. Leaded gasoline and the over-use of certain fuel additives can shorten the life of a catalytic converter.

A catalytic converter can also fail because of:

* Bad exhaust valves on the engine

* Fouled plugs causing unburned fuel to overheat the converter

Sometimes you can tell that a converter is clogged because you don't go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter. A partially clogged converter often acts like an engine governor, limiting the actual RPMs to a fast idle. A totally clogged converter causes the engine to quit after a few minutes because of all the increased exhaust back pressure.

The catalytic converter, like the rest of the emissions system, typically has a warranty length that exceeds the term of the warranty for the rest of a typical U.S. automobile.

Here is a safety reminder: Do not park your car over tall grass or piles of dry leaves. Your car's perfectly running catalytic converter gets very hot…enough to start fires! You can keep it running well by keeping the ignition system in top shape, to prevent any unburnt fuel from entering the catalytic converter.

The link I got this from:

http://auto.howstuffworks.com/question482.htm

Wow, that's a goor read, 98. :thumbsup:

Some of that sounds like my car too.

But I wondering how I could tell the difference between it being the cat or say, the IAC valve.

Though thinking about it, replacing the MAP sensor didn't help much, it didn't fix the rough idle...

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My money is on a bad cat.

Made a HUGE difference on my Maserati when I replaced its cat.

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My money is on a bad cat.

Made a HUGE difference on my Maserati when I replaced its cat.

So.. what differences did it make?? I am curious to know what to expect.

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WOW, that is a great write up from How Stuff Works. I work on developing and testing catalytic converters at work, and after reading the first thread I thought I would have to type all that up, but that write up explains it very well.

From the symptoms you are describing, I wouldn't hesitate in replacing the converter.

When cats go bad the exhaust has a funny smell. I cant really describe it, but it is noticeable.

Here is a safety reminder: Do not park your car over tall grass or piles of dry leaves. Your car's perfectly running catalytic converter gets very hot…enough to start fires! You can keep it running well by keeping the ignition system in top shape, to prevent any unburnt fuel from entering the catalytic converter.

At work, I have seen cats get up to 1000* F :fiery:

Edited by schuby87
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So.. what differences did it make?? I am curious to know what to expect.

I was thinking the same thing.

About how much does a Cat run? 100 bucks? 150?

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I was thinking the same thing.

About how much does a Cat run? 100 bucks? 150?

Depends on the car, but can be several hundreds of dollars. From what I understand mine isn't that expensive... I have a 92 Century, 3300 V6.

My mechanic told me a month ago that my cat converter was just starting to go... however, I didn't expect the symptoms I'm getting. I mean, I notice a sluggishness... just a bit. But I hear such a loud metallic rattling sound as well. Last time I heard that, it was because of the heat shield. Now, I'm also hearing a high-pitched chirping sound between 40-60mph... so I have no idea what's up.

Anyway, sorry, don't want to steal away from your thread. Let me know if you have any of those symptoms too.

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So.. what differences did it make?? I am curious to know what to expect.

Huge increase in power, improved idle quality, lower operating temperature, easier starting, etc.

In short, it ran better in every way.

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Huge increase in power, improved idle quality, lower operating temperature, easier starting, etc.

In short, it ran better in every way.

I noticed just driving it is sluggish like it going the same speed even though the speedometer is going up. The idle upon start up is horrible. and it does heat up quick too. It gets hot. When starting... oh brother.. it sounds horrible. I hope my gas mileage will go up. I drove it today, and it is sucking gas like it is going out of style. I might have to stop driving it until I can get those issues fixed. The rpms are low too. they never go past like 900 something.

Thank you Camino.....

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Huge increase in power, improved idle quality, lower operating temperature, easier starting, etc.

In short, it ran better in every way.

Now that would be nice.

I don't think I pull 200 miles out of a tank now....better gas milage would be sweet too.

This thing used to have great get up and go....

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Glad I could help, guys.

The weird part is, the 'rati only had 39k on it at the time - so I didn't suspect the cat at first.

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Really and truly the cat doesn't have a "probable milegage failure" like some parts do, you know, you more or less expect to replace a set of brake pads every 50k-80k miles, and stuff like that, you could possibly buy a new car off the lot with a bad cat. It all depends on the quality control placed on the parts when they leave their manufacturers. Although given your description, it sounds like a cat problem, considering that it is an OBD-I car, and you don't possibly have emissions inspections, you could always straight pipe the cat and let that be that.

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Really and truly the cat doesn't have a "probable milegage failure" like some parts do, you know, you more or less expect to replace a set of brake pads every 50k-80k miles, and stuff like that, you could possibly buy a new car off the lot with a bad cat. It all depends on the quality control placed on the parts when they leave their manufacturers. Although given your description, it sounds like a cat problem, considering that it is an OBD-I car, and you don't possibly have emissions inspections, you could always straight pipe the cat and let that be that.

I guess I'm lucky I got 14 years put of that cat then. I've been replacing a few parts thinking it might be a fuel issue

(Map sensor, etc) , I never thought it owuld be the cat.

Would straight piping be an issue with city driving?

I might just replace the cat- hopefully that might help.

Does a bad cat cause really rough idle?

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Well, that all depends on your state's emission guidelines. Here in Alabama, you can slice the cats off anything, there's no state-mandated emissions testing. As far as driving with one straight-piped, no difference, in fact, you may notice a slight increase in oomph when it comes down to it since there will be free-er flow through the exhaust system. And yes, a bad cat can cause a rough idle, lack of acceleration, crappy fuel mileage, a change in exhaust smell, increase engine temperatures, and eventually keep the engine from running completely.

More or less think of your engine as a big air pump, it sucks air in, compresses it, and pushes it out. If the catalytic converter is clogged up (the honeycombing inside has collapsed and blocked exhaust from getting out), then the engine can't exhale like it needs to, which means that it has to work even harder to suck air in and compress it since there's a backlog in getting it out.

Hope that this helps.

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The one thing I can help out is... The rattling... That definitely was the catalytic converter. Disappeared once it was replaced. The old cat is still in the garage and upon kicking it... It rattles. :P

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You guys are right.. They information you are giving us is correct. I found out today my Toronado has not only a bad cat, but an exhaust leak too. It is near the cat where the leak is. I will have to have the cat and the exhaust leak( pipe) replaced too. That explained the sluggish performance and the bad gas mileage and the rattling too.

The gas mileage is so bad, you would think I was driving a Chevrolet Silverado with the biggest V8.

Edited by NINETY EIGHT REGENCY
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You guys are right.. They information you are giving us is correct. I found out today my Toronado has not only a bad cat, but an exhaust leak too. It is near the cat where the leak is. I will have to have the cat and the exhaust leak( pipe) replaced too. That explained the sluggish performance and the bad gas mileage and the rattling too.

The gas mileage is so bad, you would think I was driving a Chevrolet Silverado with the biggest V8.

The wagon has v8 milage right now..... and city driving isn't helping either.

The only saving grace is that is does just local driving at the moment...as it seems to be getting worse as it has been warming up the last few weeks....

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Well, that all depends on your state's emission guidelines. Here in Alabama, you can slice the cats off anything, there's no state-mandated emissions testing. As far as driving with one straight-piped, no difference, in fact, you may notice a slight increase in oomph when it comes down to it since there will be free-er flow through the exhaust system. And yes, a bad cat can cause a rough idle, lack of acceleration, crappy fuel mileage, a change in exhaust smell, increase engine temperatures, and eventually keep the engine from running completely.

More or less think of your engine as a big air pump, it sucks air in, compresses it, and pushes it out. If the catalytic converter is clogged up (the honeycombing inside has collapsed and blocked exhaust from getting out), then the engine can't exhale like it needs to, which means that it has to work even harder to suck air in and compress it since there's a backlog in getting it out.

Hope that this helps.

Thanks.

I think I'm going to go ahead and replace the cat...I have a feeling( thanks to you guys) that it is probably the issue....

Hopefully it's not too pricey....

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