My Cat converter has given me the rotten egg smell after runnin WOT.. on a few occassions.. and I"m not accelarating right.. it seems to lag till top 1K RPM ( compared to normal ).. so I"m guessing the current cat is clogged.. but I had it replaced 2 years ago.. just wondering what would cause it to foul so quick?
Only thing I can think of is a rich setting.
I"m gettin a scan tool soon to get the reading from the 02 to see if it registers if I'm runnin rich or lean.. ( well noobie to scan tool so I"ll have to find out what the norm would be and compare ) and I have no CES ( which would occur if the 02 sensor is dead )
So other then replacing the 02 sensor also.. what else could foul up a Cat converter so quick?
I"m planning gettin a hi flo cat (carsound/magnaflow), but I don't want to keep replacing cat converter every 2 years.
Fouling Cats
- Thread starter drifter420
- Start date
- Status
it is normal for an engine to run rich at WOT.
The rotten egg smell is caused by sulfur in the fuel. It does not normally indicate a problem. Some catalytic converters have a propensity to accentuate the formation of this gas, notably Toyota converters. It usually occurs under rich mixture conditions such as WOT or cold starts.
If you have access to a vacuum gauge, run the engine at about 2000 RPM. If the vacuum gauge needle drops to a low reading and is slow to return to normal (about 17 to 20 inHg), then your cat might be clogged.
An infrared non-contact thermometer should show about a 10% increase in temperature of the cat from front to back, if it is working. If the outlet of the cat is distinctly cooler than the inlet, you probably have a plugged cat.
You are better off going with an OEM converter designed for your vehicle. After-market converters are not as well made. They have less catalyst, and they substitute more of the cheaper palladium for the more expensive platinum in the mix.
Honestly, I would not bother with a boutique high flow catalytic converter. You are asking for trouble from the get-go. OEM will save you a lot of grief.
Depends on the age of the vehicle, most pre-1996 cars didn't monitor catalyst efficiency (which is accomplished with an oxygen sensor after the cat).
I believe the cat is clogged then.. I have used a Laser Temp gun before and it's cooler behind the cat then the front.
But I was hearing conflicting story sayin that the temp should be cooler after the cat as the amount of metal would've dissapated the heat..
( I did test only basically idle and car being in park.. didn't want to free rev the engine too much.. and let it sit there idling for 5-10min. after it got to normal temp.. so it started heating above normal temp )
I don't have access to a vacuum gauge currently.. I"m assuming you're refering to checkin thru the engine's vacuum line? Or the 02 hole??
So I wonder then why the cat gave out so early?? I can't remember when I did it at the muffler shop if it was some universal OEM one or OEM
[ June 16, 2006, 10:39 PM: Message edited by: drifter420 ]
Hey brianl703, I hear you. But another problem is that changing the back-pressure will affect the EGR system. Some EGR systems are very sensitive to this. On OBDII cars you might start seeing P0401 and related codes. Also cars with pulse AIR may mess up the air injection if you mess with the back-pressure. TurboJim has a good point about possible problems, but I certainly understand your point about pre-1996 vehicles.
My own opinion is that real old-time hot rodding is dead. A guy almost has to have access to a lot of expensive test gear like dynos and emission machines. If someone loves hot rodding, then it might be best to move to a rural area without emissions scrutiny. And if someone lives withing 50 miles of a big city, sprawl means that even if your car can go fast, traffic congestion sort of takes the fun out of it. All dressed up and no place to go.
drifter420 writes
quote:The main cause of premature catalytic converter failure is overheating usually due to engine misfire. The OBDII refers to a "Type A" misfire as being the worst for your catalytic converter. If you see your "Check Engine Light" blinking then it means that the PCM has detected a "Type A" misfire, that is a misfire that will cause imminent overheating of the catalytic converter and subsequent failure. The problem with a misfire is that instead of burning up in the combustion chamber, all that raw unburned fuel will burn up in the cat. Anything that can cause a misfire such as vacuum leaks, exhaust manifold leaks upstream of the O2 sensor, or a bad MAF sensor should be fixed. Leaking injectors can cause problems as well as burned exhaust valves. Another cause of catalytic converter overheating is air injection being applied at the wrong time, such as during rich conditions like cold starts and WOT. A bad diverter valve can cause this. Leaded fuel will poison a cat, as will excessive oil burning. Ethylene Glycol coolant from a leaking intake manifold gasket or bad head gasket will do a number on a catalytic converter. Snake oil "octane improvers" are anther way to poison a cat. And then there is old age. Catalytic converters can just get old and worn out. [ June 16, 2006, 10:41 PM: Message edited by: vizvo ]
" . . . what else could foul up a Cat converter so quick?"
Wow.. didn't know so much could mess up a cat converter.
When I get my scan tool next week.. anyone know or can help noobie decipher my 02, MAF readings to let me know if it's either of them ( I think it'll do injectors also.. again.. noobie to scan tool )
I will have to go to my bro's and check for any vacuum leaks. ( he's got a vacuum gauge )
Incidently.. after I used a bottle of Gumout Regane maximum.. I don't get the rotten egg smell anymore ( maybe either the cat was clogged beyond stinkin it up or maybe cleaned some of the carbon out around the valves??.. )
On another side note.. my mechanic did check the readings on the rear 02 sensor ( after cat ) and it doesn't move.. no voltage fluctuation ( the front does ) so he's sayin either my cat is dead or the rear 02 sensor is gone.
The story on MOTORVAC cleaning the BMW 320 is of interest, (long first post, here), perhaps:
http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=33;t=002148;p
Hey drifter420, the Gumout Regane might have helped. If it cleaned up carbon on the exhaust valves it could help them seal better. It's hard to say exactly what it might have done to the cat; maybe it helped.
One other thing that bears mention is that a plugged muffler or tail pipe could cause the same symptoms as a plugged cat.
quote:That sounds like a bad cat. You might want to retest you catalytic converter with the Laser Temp gun after 15 minutes of spirited driving, including some hard acceleration. You want to make sure that cat has a chance to light up. Oh, and one drivability symptom of a plugged cat is that then engine bogs down under load, like hard acceleration or climbing a hill.
"I believe the cat is clogged then.. I have used a Laser Temp gun before and it's cooler behind the cat then the front."
quote:I'm not sure what your mechanic is saying, but on the face of it he appears to be dead wrong. If you were take a lab scope and look at a good catalytic converter, the front sensor should show a lot of activity switching from high to low, while the rear sensor should look like it was a "flatliner". The rear sensor should have a relatively flat output with little fluctuation. I suppose if the cat was completely plugged, then maybe you'd get a flat line too. A lot of voltage fluctuation on the rear O2 sensor means that the converter is not working efficiently. It is far less common for the rear O2 sensor to go bad compared to the front one. If your brother is a good sport, and has a compression gauge, you might want to ask him to do a compression check on all the cylinders. It could help you spot a burned or leaking valve. Also with the vacuum gauge you should have him quickly raise the RPMs to about 2000 RPM. Hold it there and watch the needle. If it drops to a low reading and is slow to climb back up, then you might have a restricted exhaust, either a plugged cat or muffler. At plain idle you should have about 17 to 20 inHg of steady vacuum on a good engine. It would help us if you supplied some more information, such as year, make, model, engine size, pertinent history of the vehicle. Keep us posted. Good luck.
"My mechanic did check the readings on the rear 02 sensor ( after cat ) and it doesn't move.. no voltage fluctuation (the front does ) so he's saying either my cat is dead or the rear 02 sensor is gone."
It's too hot right now to do anything.. will check with laser temp gun tomorrow..
Sorry.. it's a 1997 Pontiac Bonneville SSEI L67 3.L Supercharged
The car went swimming a few years back and killed the original Cat ( hot burning cat meets ice cold winter water.. ) So the original cat was hollowed out when I replaced it.. nothing in there at all..
Changed cat 2+ years ago. Got the egg smell around spring this year.. first sign was also my temp would climb quicker when idleing and stopped bout the same time. Getting scan tool end of next week.. So I"m debating whether to just go and change cat now or wait till I get scan tool first
quote:Not needed to pass emission.. My car is registered up north so I don't have to worry bout emission test. I just want to fix it ( before it breaks and burns something else out and cost more $$ in the long run ) I guess the most economical way of doing it is to put the hollow cat back in.. but my hippie tree huggin side would feel guilty
Originally posted by vizvo: You definitely want to diagnose any problems before replacing the catalytic converter. It would be a real pain in the wallet to replace the cat, and have it meltdown in a couple of weeks. That supercharged Bonneville was a nice car straight from the factory. I don't know what the emissions laws are in Canada. Are you trying to get the car to pass an emissions test, or are you just trying to fix it so it runs OK? If running a hollowed out cat is legal in Canada, you could do that and buy one of those dummy rear O2 sensors which fool the PCM.
![[LOL!]](/forums/graemlins/lol.gif)
![[No no]](/forums/graemlins/nono.gif)
You definitely want to diagnose any problems before replacing the catalytic converter. It would be a real pain in the wallet to replace the cat, and have it meltdown in a couple of weeks.
That supercharged Bonneville was a nice car straight from the factory.
I don't know what the emissions laws are in Canada. Are you trying to get the car to pass an emissions test, or are you just trying to fix it so it runs OK? If running a hollowed out cat is legal in Canada, you could do that and buy one of those dummy rear O2 sensors which fool the PCM.
- Status
