Broken up Catalytic converters after 4k miles?

RichM

Registered User
What would cause my catalytic converters to break appart inside after only 4000 miles?

The motor was rebuilt with a 0.030 overbore using stock type parts (hyperutectic pistons, i.e. nothing fancy) less than 4000 miles ago.

Other mods are:
  • Removed intake silencer
  • K&N panel filter
  • 73mm C&L MAF
  • port and polished supercharger intake plenum
  • Magnuson S-port blower
  • Port matched intake manifold
  • polished heads (no porting, no bowl work, no chamber work)
  • 38# injectors
  • 190 lph fuel pump
  • Kook Mid-length headers
  • Supercoupeperfromance.com downtubes w/ hiflow cats
  • Supercoupeperfromance.com 3 inch cat back exahust
  • New Double Platinum plugs 0.045 gap, now Magnacore wires,new O2 sensors (all from Supercoupeperformance.com)
Non-Mods or "stuff I've left stock for now"
  • Stock Airbox
  • Stock Throttle body
  • 91 size supercharger pulley
  • Stock IC and Tubes
  • Stock valves
  • Stock Cam
No unusual oil consumption
Coolant level stable/normal
engine temperature normal
No "rotten egg" exhaust smell
No raw fuel smell in exhaust either
Gas milage between 18 and 23mpg mixed highway and city driving
Car ran great after rebuild, no backfiring or bad missing.

I'm pulling the plugs this weekend to read them, But I don't expect to find anything really wrong. I have a new fuel filter to replace the one that is a year old in case it got plugged when I swapped the fuel pump.

Engine codes are for SPOUT grounding and TPS voltage lower than expected. New DIS and TPS on the way, should be here monday. Crank sensor was replaced with engine, Cam sensor was replaced when SPOUT Grounding code was first seen many years ago with no effect.

I'm stuck in a catch22, The muffler shop won't warentee the replacments unless I "fix whatever caused the original cats to disinigrate". The other shop won't do a diagnositic on the car with the exhaust plugged from the broken cats, and I don't have the equipment to do the ignition system diagnostic myself
 
maybe you accidentally hit it along the way? My cat broke apart the other day after I messed around with the exhuast, it was about 3,000 miles later when I heard the clanking.
 
I'm stuck in a catch22, The muffler shop won't warentee the replacments unless I "fix whatever caused the original cats to disinigrate". The other shop won't do a diagnositic on the car with the exhaust plugged from the broken cats, and I don't have the equipment to do the ignition system diagnostic myself[/QUOTE]

is your car running rich? Your gas mileage sound about right so I would not think so.

I bought some Catco CTO-6906 from summit About $200 by the time I had them installed. I had the SCP cats before but they were second hand.



http://www.sccoa.com/forums/showthread.php?t=46465&highlight=catco
 
Rubbin

Take a close look at the exhause and be positive it isn't rubbing anywhere when the engine is under a lot of torque. The exhaust can move by up to an inch (even more if motor mounts are toast). If it's rubbing and rattling against anything, could be part of the problem.

This happened to me after I had my exhaust rebuilt the first time. It was fine sitting on the rack, but it was getting beat up when I drove it.

good luck
Bob
 
RichM said:
What would cause my catalytic converters to break appart inside after only 4000 miles?

The only thing I can think of is that your car is running lean and there was too much heat going through the cats? :confused: You haven't been running Avgas through your car have you? :D
 
You might want to get a dyno tune or a chip? You have changed injectors and maf without recalibration.
 
scbird1 said:
You might want to get a dyno tune or a chip? You have changed injectors and maf without recalibration.

Hmm, many other people have added the 73mm C&L and larger injectors without having to reprogram the computer. I'm not to comfortable with putting a questionable car on a dyno. I was going to dyno it in a few weeks when this happened. Hopefully I can get the cats replaced and work on those CELs, then take it to the dyno.

MartianBob said:
Take a close look at the exhause and be positive it isn't rubbing anywhere when the engine is under a lot of torque. The exhaust can move by up to an inch (even more if motor mounts are toast). If it's rubbing and rattling against anything, could be part of the problem.

Didn't notice any tattletale rub marks. The mounts are new solid rubber ones, not the stock hydraulic ones.

Darkside said:
The only thing I can think of is that your car is running lean and there was too much heat going through the cats? You haven't been running Avgas through your car have you?

Damn Darkside, you know I don't do that. I only use Monomethalhydrazine, it's easier to get at work. All joking aside, straight 91 octane pump gas. I don't even add anything to the crap we get in NM.

Tony8470 said:
maybe you accidentally hit it along the way? My cat broke apart the other day after I messed around with the exhuast, it was about 3,000 miles later when I heard the clanking.

I didn't notice any damage, I'll check when it on the lift.

wezar said:
is your car running rich? Your gas mileage sound about right so I would not think so.

No luck wezar, plugs look good to me. The insulator is actually cleaner than I expected.
plug.jpg


I got the new DIS and TPS today. So they will go on this weekend after I pull the codes again. Then clear the codes and take it over to the shop for a full diagnostic. Then, off to the muffler shop with all the receipts and hope the guy will gaurentee the cats. But I figure it they break again the isn't going to warentee it anyway.
I also need to do a propane check of the intake. Just one more thing on the endless T-bird list.

Thanks guys, if you come up with anything else pipe up.

RichM
 
where they damaged prior to install?

Ive taken cats off some vehicles and cleared them and it isnt easy to get all that crap outa there,beating and hammering with rods and such so i find it hard to believe that a little over heat or lean burn or rattle could do this type of damage
Vetteman




89 SC 5 spd
76 vette
84 vette
87 vette
70 GT torino
 
Shockwave said:
What color sample tube are you using with the 73mm C&L?


Jerry

Blue sample tube. double checked this already.

Per the C&L web page
http://www.cnlperformance.com/calibration.html
Std Fuel Injector (30 for 89-93), (36 for 94-95) Clear Tube (101)
36lb Injector (89-93 processor) Blue Tube (102)
42lb Injectors (89-93 processor) Red Tube (103)

I took a timing light to all the plug wires and found that my #5 cylinder isn't firing consistently or at all, But when I wiggle or push on the connection at the coil pack it starts to fire again. Looks like I have a bad wire on the #5 cylinder. This still doesn't explain the passenger side cat being broken apart. Still hunting, I'm in the middle of replacing the TPS but those damn screws are seized.
 
RichM said:
I took a timing light to all the plug wires and found that my #5 cylinder isn't firing consistently or at all, But when I wiggle or push on the connection at the coil pack it starts to fire again. Looks like I have a bad wire on the #5 cylinder. This still doesn't explain the passenger side cat being broken apart. Still hunting, I'm in the middle of replacing the TPS but those damn screws are seized.

Update:
Well replaced the DIS, and the TPS. Looks like this might actually get rid of my CELs. But I swapped the Magnacore wires out for an old set of Taylors to see if it was the wire on the #5 cylinder. Didn’t help. cyclinder balance test keeps coming up cylinder 5 down on power.

I don't know if it's the induction type timing light or my ignition system, but the firing of the coils seems almost random at times. On just about all wires sometimes it fires good and steady, sometimes it doesn't show a firing at all and sometimes it's shows really fast firing. I'm at the end of my capability to diagnose this problem so off to a shop with some better diagnostic equipment she goes.

I need to find a daily driver/beater car instead of my SC.
 
Well if #5 shows bad on the test it's either spark, fuel, or air. You need to determine three things on number 5 cylinder:

1. compression of #5
2. Spark plug and wire condition for #5
3. condition of the #5 injector


Tests
1. Compression You can buy or rent a compression gauge and get actual compression of #5 and compare to the others on that bank.


2. Spark If you have another set exchange out that plug wire. You can also measure the resistance of the #5 wire and compare to the another wire. The coil pack is made up of three coils with each one firing a pair of cylinders. So you can rule out the coil. The DIS, CAM, Crank Sensor would not cause a problem with only one cylinder so you can rule those out. You can also swap out a spark plug from another cylinder and switch with #5. If a different cylinder shows bad on the balance test you will know where the bad part is.

3. I have used a stethoscope to listen to injectors to tell if they sound right. By comparing to the others you can sometimes tell a bad injector. You can check for a leaking injector by how quickly the injector leaks pressure off after the key is turned off. Install a gas pressure gauge on the test Schrader valve on the fuel rail and measure fuel pressure. Fuel pressure with key on and engine off should be around 43 PSI. With the engine running pressure should be around 39 PSI. With the engine off the pressure should hold for over 15 minutes. If pressure falls off fast you have a leaking injector.

I don't think CATs can be hurt by the engine unless you are really rich, and I can’t really see where running lean can hurt them. Unburned gas will burn in the CAT and can burn it up. The question is how can one bad cylinder burn both CATs up when they are fed different engine banks?

Don't give up!

Jerry
 
Shockwave said:
I don't think CATs can be hurt by the engine unless you are really rich, and I can’t really see where running lean can hurt them. Unburned gas will burn in the CAT and can burn it up. The question is how can one bad cylinder burn both CATs up when they are fed different engine banks?

Don't give up!

Jerry

I am going to pick up a cheap set of fresh plugs this afternoon and give that a try, maybe my #5 cyclinder problem is a cracked insulator. Something just doesn't sit "right" with me about when i pulled the plug. I'm hoping that it is something as simple as a cracked insulator.

I already tried a different set of wires with no difference. So I can swap the Magnecore's back on (The Taylor wires are pink... I just can't stand that).

Now the current theory on "why both cats died at the same time", maybe a lean condition caused by a dirty MAF sensor. I know it's a stretch, but the cats disinigrated over a matter of a week (about 250 miles) and a lean condition could have caused the plug to overheat and crack and might have caused the cats to overheat. It makes some sense.

Don't worry about me giving up, I have spent far too much time and money on the bird in the last 6 months (rebuilt engine, rebuilt tranny, headers, etc etc) to just trade it in on some econo box. I couldn't get half of what I have sunk into it back out if I sold her. I am contemplating picking up another car so that I have something a little more reliable. That way I can also elevate the T-birds level to "pure toy" instead of "daily driver".
 
Kurt Sunday said:
Hey Buddy - i got a new cell... please call me and leave me your numbers.

Kurt, I thought you where actually working and too busy to answer my calls. I'll give you a ring tomorrow sometime and leave my numbers.

One more think Kurt, Pony Carburetors is having a dyno day on August 21st, 2004, First come first served, 8am to 1pm. 40 bucks a pull! Person with the highest hp/cubic inch gets there pull for free. I haven't found out if they have a wideband O2 yet, but I will. Not that I expect them to have that up and running on the dyno day.

For everyone else, Ponycarburetors.com 112 Westgate Street, Las Cruces NM.

Now the update;

Well it's amazing what a broken spark plug will sound like. I never knew something that small could make that much noise. Even fooled a seasoned exhaust guy. Or so it seems, replaced the plugs and the rattle sound went away.

plug2.jpg


But swapped out the plugs with a set of cheapo copper autolites and the sound went away, I'll look for a set of Denso plugs in the near future. The cylinder balance test came up roses, but during the "key on engine running" test the computer reported a rich condition that I will have to look into. Nothing bad enough to cause a check engine light to come on. And since it was during the engine balance test, it could be normal.

Luckily, since the noise went away I am under the impression the cats are still moderately ok. Also a funny thing, when I pulled the plug Saturday it was nice and clean (same plug that I have pictured above) now it's fouled beyond belief.

Does anyone know if the computer keeps the injectors from firing during a cylinder balance test? Or does it just pull the spark? That might explain the rich condition during the test.

I also got a 225 error code "Knock sensor fault during dynamic response test". Might this be normal or am I somehow running too much timing, too low an octane, cheapo plugs (see above)?
 
Are you saying that the CATs are ok? I don't follow you. When you said that your CATs were bad, I thought you meant they were cracked up and you knew that to be a fact. Very confusing for people trying to give advise.

The knock sensor failed is usually from operator error during KOEO (Key On Engine Off) in that you didn't mash the throttle hard enough or fast enough during dynamic response or failed to do it at the right time.

I'm also not sure what you meant by a rich code during balance test. Rerun the codes and let us know what the code numbers are. I'm 99% certain that the balance tests shuts off the injector not the spark.


Jerry
 
Shockwave said:
Are you saying that the CATs are ok? I don't follow you. When you said that your CATs were bad, I thought you meant they were cracked up and you knew that to be a fact. Very confusing for people trying to give advise.

It seems so. When this started, there was a loud rattling sound coming from somewere under the car, the sound could not be heard from the engine bay. So I took it to a muffler shop and had them put it up on the lift and check it. The muffler shop, suposidly one of the better ones in this town, said both catylitic converters where broken appart inside and needed replacement. But, when I replaced the spark plugs the rattling sound stopped.

The cats may still be broken up but they are not making the rattling sound anymore. The exhaust is back to the same tone as when I first put the engine in, the power delivery back to normal and I have no "keep in memory" codes (i.e. Check engine lights).

Shockwave said:
The knock sensor failed is usually from operator error during KOEO (Key On Engine Off) in that you didn't mash the throttle hard enough or fast enough during dynamic response or failed to do it at the right time.

The written procedure I received with the code scanner states to press the accelerator 1/4 way down to start the cyclinder balance test. It's rather specific about not touching the accelerator until the test is complete and the codes are transfered to the reader, so I just camped out by the code reader and away from the accelerator and didn't touch the throttle linkage. I have not done a dynamic responce test yet, only the cyclinder balance test.

Shockwave said:
I'm also not sure what you meant by a rich code during balance test. Rerun the codes and let us know what the code numbers are. I'm 99% certain that the balance tests shuts off the injector not the spark.

I don't have the code scanner with me right now. I'll have to confirm the exact codes when I get home. But from what I remember, during the "cyclinder balance test" I received code 225 "Knock sensor fault during dynamic response test" and code 173 or 175 but I don't recall exactly what it translates, but does state a rich condition according to the HEGO sesnor (O2 sensors).
 
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Shockwave said:
The knock sensor failed is usually from operator error during KOEO (Key On Engine Off) in that you didn't mash the throttle hard enough or fast enough during dynamic response or failed to do it at the right time.

I'm also not sure what you meant by a rich code during balance test. Rerun the codes and let us know what the code numbers are. I'm 99% certain that the balance tests shuts off the injector not the spark.


Jerry

Ok, the codes I reveived during the cyclinder balance test:
173 HEGO sensor fault rich
225 Knock sensor fault during dynamic response test (this is my fault, I probibly jumped into the cyclinder balance test early)

On the way home from work I got another code,
124 TPS voltage above normal

It's a new TPS and I checked the voltage; 0.88 at idle, 4.83 at WOT. Hot idle is at 750 rpm.

Ran the dynamic responce test this afternoon and received the following codes:
173 HEGO sensor fault rich
137 HEGO sensor fault, always rich
225 Knock sensor fault during dynamic response test

The car acted different at part throttle than I have expereinced in the past. It ran scary fast at part throttle.

I haven't been able to find a high pressure fuel guage to test the injectors for bleed down. I guess the engine is running very rich acording to the computer, but the plugs read as being fine. So, maybe the O2 sensors?

Any idea's?
 
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What is the situation with the CATs? Are they broke up, burned up or fine? Were you just hearing the noise from the cracked spark plug and thinking it was the CATs?

I did a quick look up over at mn12performance EEC codes and 137 (left side) and 173 (right side) are O2 sensor indicating rich.

The .88 volts on the TPS is about perfect. The only thing you can do is actually have the engine running and check it, this might change things a few tenths of a volt due to the higher than 12V battery voltage from the alt. Make sure the throttle isn't sticking open slightly or anyting.

When I do a Key On Engine Running test my Autoxray goes from scanning to dynamic response, at that time I do a quick snap to wide open throttle. It might seem hard on the motor to jam it to WOT, but it works the knock sensor so it can be checked.

I would clear all the codes and drive the car some more. If the O2s were good and the car was running rich for whatever reason, I would think you would get a code like adaptive fuel lean limit reached. If the codes comeback and you have never changed out the O2s then do that.


Jerry
 
Shockwave said:
What is the situation with the CATs? Are they broke up, burned up or fine? Were you just hearing the noise from the cracked spark plug and thinking it was the CATs?

Thanks Jerry,
The cats: At this time I suspect they are poisoned, but not broken down yet (it's only a matter of time).

Shockwave said:
The .88 volts on the TPS is about perfect. The only thing you can do is actually have the engine running and check it, this might change things a few tenths of a volt due to the higher than 12V battery voltage from the alt. Make sure the throttle isn't sticking open slightly or anyting.

TPS voltage at idle (engine running): 0.90 volts engine running, 0.90 key on engine off. Thank god it isn't the sensor driver in the computer. I blipped the throttle a few times and it came back to 0.90 each time.

Shockwave said:
When I do a Key On Engine Running test my Autoxray goes from scanning to dynamic response, at that time I do a quick snap to wide open throttle. It might seem hard on the motor to jam it to WOT, but it works the knock sensor so it can be checked.

The dynamic test: I need to buy an extention cable for my cheap little 50 dollar code reader. Neighbors must have thought I was nuts dacing around the car... or they thought I was performing an excercisim, which is close... I may have messed up the dynamic test.

Shockwave said:
I would clear all the codes and drive the car some more. If the O2s were good and the car was running rich for whatever reason, I would think you would get a code like adaptive fuel lean limit reached. If the codes comeback and you have never changed out the O2s then do that.

The codes: I cleared the codes and reset the computer lastnight. No codes so far, with 50 additional miles on the clock. The code table that came with the scanner is not as exact as the codes from MN12. I downloaded those codes a while back. After I dug them up I realized that the 173 and 137 codes where from different banks.

I really wish I had more information on what is envolved in some of the engine running tests. That might help explain what codes to expect as normal during the test. For example, if during the cylinder balance test the computer just pulls spark from specific cyclinders but doesn't shut down the injector a rich condition will happen, and can be expected. But if the computer pulls the injector and the spark, or injector only, then a lean condition can be expected. Just adds some spice to life I guess.

The O2's are new from the rebuild, 4000 miles. I do realize they can get burnt up in a matter of seconds if the wrong conditions precist.

I need to read though my Helm's and see if there is a manifold pressure sensor. I think if the computer compares the intake pressure to the TPS signal during the check that would cause the 124 code. A bit more reseach is in order. I don't even know if the car has an intake pressure sensor.
 
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