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Always - no, wait - Never Trust Your Original Catalytic Converter by blainelocklair
Started on: 04-19-2014 01:19 PM
Replies: 7 (752 views)
Last post by: theogre on 04-20-2014 10:39 AM
blainelocklair
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Report this Post04-19-2014 01:19 PM Click Here to See the Profile for blainelocklairSend a Private Message to blainelocklairEdit/Delete MessageReply w/QuoteDirect Link to This Post
While trying to diagnose my previously poor running Fiero, I learned that my original catalytic converter looked like this when I removed it:



Just a quick note for future searchers that, in my experience, my original catalytic converter was completely clogged with water and carbon buildup. If you're diagnosing poor running / stalling conditions with your engine, don't overlook this simple part. What is the easiest way to start to suspect a clogged cat? In my case, it was poor exhaust flow at the exhaust tips, which I had overlooked as a possible cause for my poor engine performance.

Hope this helps someone down the road someday. I posted this info in my original thread, but it sort of got lost in the many troubleshooting strategies.
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Patrick
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Report this Post04-19-2014 04:47 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post

And don't trust your aftermarket cats either...



Pulled that off my '86 GT a few years ago.
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Lambo nut
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Report this Post04-19-2014 06:31 PM Click Here to See the Profile for Lambo nutSend a Private Message to Lambo nutEdit/Delete MessageReply w/QuoteDirect Link to This Post
On a different car, but one of my brothers had a problem with his 88 EXP running like crap. Turned out the cat was plugged. We made it "unplugged" and it ran like a top!!

And second, I know who you were alluding to in your title!

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steve308
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Report this Post04-19-2014 08:49 PM Click Here to See the Profile for steve308Send a Private Message to steve308Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yep - After 25+ years of steady service I had to hammer tune my converter shortly after returning from Carlisle last year, almost didn't make it over the mountain on the way home due to the clogged converter.
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theogre
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Report this Post04-20-2014 01:54 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:
And don't trust your aftermarket cats either...

Pulled that off my '86 GT a few years ago.

In many cases, that damage cause by replacing the cat but not fixing other problems.
Burning oil, rich engine, leaking coolant from bad head, etc can overheat "plug" or poison the cat.

<Edit>
 
quote
The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F. But as the amount of pollutants in the exhaust go up, so does the converter's operating temperature. If the temperature gets up around 2,000 degrees F or higher, several things happen. The aluminum oxide honeycomb begins to degrade and weaken. The platinum and palladium coating on the honeycomb also starts to melt and sink into the ceramic substrate reducing its effect on the exhaust. This accelerates the aging process and causes the converter to lose efficiency.

If the overheating condition persists for more than a few minutes, or if the temperature soars high enough, the honeycomb itself may melt forming a partial or complete obstruction, causing a sharp rise in backpressure. A complete blockage will cause the engine to stall shortly after starting, and will not allow exhaust to exit the engine.

Source: www.aa1car.com/library/converter.htm

Overheat is a big fire hazard. Can easily ignite grass/leaves you park over or burn down the car.
</edit>

blainelocklair is not OE either.

GM OE Fiero and many others are big flat "pellet" type and have a plug in bottom. Plug is how the pellets/beads are loaded. Used to be you could reload the beads when cat got poison. Bead types can die when the "cage" is rusted out.

source: www.highperformancepontiac....me_restorations.html

Edit to add> My Fiero OE cat is 25+ years old and still passes DE emissions with very low numbers. (sniffer at idle and 2200rpm, no rollers.) I had old Fords 10-15 year old cat and passed w/ low numbers too. Only fail test on one Ford was perform when cat cold. Drive a bit and it passed 2nd test same day.

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[This message has been edited by theogre (edited 04-20-2014).]

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fierosound
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Report this Post04-20-2014 09:23 AM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageClick Here to Email fierosoundSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
The new ones are are much more efficient, flow better and less prone to clog (unless the cores melt).

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css9450
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Report this Post04-20-2014 09:41 AM Click Here to See the Profile for css9450Click Here to Email css9450Send a Private Message to css9450Edit/Delete MessageReply w/QuoteDirect Link to This Post
My original cat flowed like crazy! Someone (a certain now-defunct central-IL Fiero shop) cut the top off, gutted it and welded the top back on. It was completely empty! And you couldn't see the welds looking up at it on a lift.

I installed one of Rodney's cats and it passed emissions with flying colors each time until Illinois stopped sending notices for pre-OBD2 cars a few years ago.
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theogre
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Report this Post04-20-2014 10:39 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierosound:
The new ones are are much more efficient, flow better and less prone to clog (unless the cores melt).

Is true but not the main point.
My case... OE Fiero cat is good to pass and I don't have money to get new when old one works. I'm not driving enough to see any MPG improvement, if any.

Note that many here says zinc (ZDDP) in motor oil is good for engine but ZDDP adds phosphorus which is bad for catalyst life. Adding too much, like using aftermarket additives, can kill the cat in a hurry (edit to add> ) especially when engine burns oil.

[This message has been edited by theogre (edited 04-20-2014).]

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