...so it's toast (literally!) Another reminder that it's not a good idea to disconnect your cat ECU's!!! I had a cat failure Sat. night, driving on the 405 at 3 in the morning, the slow down 5-8 came on, car switched into "limp" mode (i.e. turned the left bank off), and I exited and pulled into the nearest parking lot. Opened the engine lid, the left cat is glowing red hot!!! SOoo... did anyone go to straight pipes / high flow cat and still has a used cat (left side or both) sitting around that I could purchase? Thanks all!
I wouldn't necessarily say that your (overheated) cat is "bad" yet (it might be, but it also might still be OKish). What you need to find out is why your ignition on that side is not working (which causes the raw fuel to be ignited in the cat), or maybe why extra fuel is being dumped on that side (i.e, the cat overheating is usually the result of another problem and not the cause). If the matrix inside the cat is unmelted/unbroken (i.e., there is no extra flow obstruction) I wouldn't worry about it. To get a look at the "input" side of the cat matrix you can remove the O2 sensor, and there might be an "inspection plug" you can remove to get a look at the "exit" side of the cat matrix (of course if you remove the cat you can inspect more easily) -- just a thought before you go thru the expense of replacement (although cats do generally self-destruct over time even when things are working properly).
Steve is correct - your engine is dumping unburned gasoline into your exhaust system, and your headers/Cat is igniting the fuel causing a "Cat Fire". If not caught in time, the rear of your car catches fire and burns uncontrolled once the fire reaches your fuel tank.....serious stuff! From what I've read on the boards, the problem is Ignition related - a bank of cylinders is not firing, and the exhaust stroke of the pistons is sending the un-ignited air/fuel mixture into your exhaust - there, ambient heat will ignite the mixture and you have uncontrolled combustion in your exhaust. Dropping the Cats in your car will help prevent a fire (by removing backpressure in the exhaust and venting the unburned air/fuel mixture away from the engine/headers), this does not fix the root problem. I wouldn't drive/start the car until you do.
Reiner I tend to agree with the others - your hot cat is more likely a symptom of a "disease" elsewhere. I suspect you know the drill - pull the codes from the 5-8 ecu to find out why the car went in to limp mode and then see about fixing that problem. Cats wise you might check with Michael at Ferrari Service of Costa Mesa (ferrariservice.ws) as he parts cars and may have a used cat. Mine were punched so were junk - maybe this is a good excuse to get a set of Hyperflows (?) I love mine with the Tubi. Cheers Kevin
Thanks for all of your advice. I have a challenge exhaust on my car, so going with straight pipes would not be an option (too loud)! I'm already talking to Michael and T. Rutlands, they seem to have used cats. According to them, these cats do go at some point...
#1 Don't ever admit to having put on a used cat, it is a serious violation in Ca. #2 Yes cats do go at some point but glowing red is not a symptom of a cat going bad, it is the cause. You still have to figure out why.
Hmmm, now I'm a bit confused. Car ran fine, then 5-8 light came on, then bank was shut down. My understanding is: cat overheated first, based on temperature (>900) 5-8 comes on, blinking, then (right away) 5-8 stays on solid, then bank shuts down. this means: cat overheated BEFORE the bank was shut down, right? But the car ran fine with full power and no check engine etc. until then.... Well I'll dig in tonight. Obviously SOMETHING caused the cat to overheat. Now I heard that sometimes these cats just die of "old age" and disintegrate, thereby impeding airflow and causing the overheating. Then, replacing the cat should solve the problem. Rifledriver, you seem to have some experience here, what would you say are common other reasons for this to happen: 1) bad O2 sensor? 2) bad ignition (wiring) 3) bad air flow meter 4) bad computer?
If your cat overheated (and I congradulate you on having the good sense to stop, get out, and give it the visual look), but without power loss, this is the other (more difficult) case where the injection system is metering out too much fuel (rather than the dead bank ignition problem).
Any of the above as well as many other things. The scenario for failure you describe in terms of disintegration then plugging the exhaust to the degree required to cause an overheat should have been in conjunction with a noticeable loss of power. I have seen many, many cats disintegrate to the point of almost complete plugging of the exhaust flow with no indicated overheat or an overheat not sufficient to be noticeable. What I and many others have seen in the vast majority if not every serious overheat was an engine problem that initiated it. Cats do wear, and they fall apart and rattle or plug the exhaust, but when they glow red hot they are getting unburned fuel from somewhere. Personally, if it were in my hands I would start the motor and warm it up and stick an exhaust analyzer on that bank pre-cat and see what the co/hc numbers were and start from there. If you don't have one of those handy, pull the plugs from both sides and compare them. The problem with the latter suggestion is two fold, if the right cat isn't working and the problem is effecting the entire motor they may look the same, the other is you may be looking for something that will cause too subtle a difference in plugs for a casual inspection to show (but I doubt it). In any event I think some serious diagnosis is in order to prevent it from happening again.
No, that's not necessarily the case. The cat got hot because an ignition component failed (could be a single wire or plug), or excess fuel was introduced into the cylinder. In the meantime, the engine controls only see an O2 sensor reading wrong (LEAN if a cylinder quits firing, RICH if there's just a lot of extra fuel going in). So it may try to adjust fueling, but doesn't correct something like a bad plug or injector. Then the thermocouple in the cat detects the overtemp and shuts you down. blah blah blah, that was pretty boring, wasnt it?
Actually, no it wasn't, and that's my understanding too. Well I took the cat out, visually inspected and it looks fine, no rattle etc. , I inspected the spark plugs in the left bank and they look light brown so seem fine, I replaced the O2 sensor with a spare one I still had, put everything back together and the car starts up and runs fine in open loop mode (i.e. cold), both banks, engine seems to have full power. So I guess the only way to go will be to hook it up to the service computer and get a diagnostics check. I'll keep you posted.
Reiner, Sorry to piss people off but I don't think these are the answers. A plugged cat from a failing piece of honycomb cat gut can wedge itself in a bad spot so as to plug the cat. This all by itself can upset fuel flow and exhaust flow causing the glowing burnt cat not and intrinsically bad part such as speculated by other posts. Just relax and change out your cat and you car will run fine. If you want to prove me right come on up to my house and swap out your bad cat for one of my punched out cats and lets see if your car runs fine. I bet it will. I'll be home allday Sunday and friday and the later half of saturday. Also the punched out cat is restrictive. So running a punched cat is louder but not as loud as say my straight pipes. I bet you could get away with it. The try is cheap and takes about 30 mins to swap out the cat. Don't worry about exhaust donuts I have a trick for that too that will make you laugh.
No doubt that taking the cat out of the system will fix the problem as my understanding of the 348 (recognize, of course, that I'm a 308 owner so I haven't seen the nitty gritty of the system) is that it uses a thermocouple in the cat to shut down the banks. So if you take the cat out, it won't burn fuel in the cat, so no shutdown! I say the trick is what happens with a cat in place! Reiner, when you looked at the cat, did you look down into the honeycomb to see that it's still nice & square? The 348 cats still don't have the crazy diffuser cone in it like my 308 did, whereby you CAN'T SEE the inlet side of the matrix, I hope.
fatbillybob, I think I agree that punching the cat out will solve this problem one way or the other (plus I've always wanted to punch out a cat anyways ), BUT: does it prove that my cat was faulty? I think not. the correct test would be to replace it with another cat and see what happens, no? Straight pipes with my challenge exhaust is too loud, and there is the smog test issue... sooo, do you still have an intact cat we could swap mine for? BTW, I did notice a few weeks back that there was quite a bit of white residue coming out of the left muffler... I heard that is a sign of a cat going bad?
I thought about this some more. the cat exhaust gasket before the O2 sensor on the left side was pretty loose (old+worn). could it be that it sucked in additional air, so the O2 registered a lean mix so it told the CPU to send more gas? So maybe this is a $2.50 fix, get new gasket reassemble and done?
Ooh, this is huge. For one, the white stuff coming out the tailpipe COULD INDEED be catalyst honeycomb material, visual inspection of the honeycomb is warranted. The reason for a cat structural failure might be related to that gasket; an exhaust leak can suck in fresh air between pulses, either throwing off the O2 sensor or by providing Oxygen for combustion of unburned HC in the cat. At this point I'd say to inspect what you've got, ensure the integrity of the exhaust system and go for a drive!
That could certainly do it. I have also seen several 348's have cat overheats as a result of the air injection system continuing to provide air after the motor has gone to closed loop.
Reiner wrote: ""I thought about this some more. the cat exhaust gasket before the O2 sensor on the left side was pretty loose (old+worn). could it be that it sucked in additional air, so the O2 registered a lean mix so it told the CPU to send more gas? So maybe this is a $2.50 fix, get new gasket reassemble and done?"" Actually, No I don't think so. 1) If it could be so easy to trick your O2 sensor to push more fuel we weekend racers would love to capitalize and trick the system for some extra power. There is just not enough fuel control via the o2 sensor. These cars run very clean in open loop by design. The close loop runs it even cleaner. When I go to the smog guy I'm allowed for my year in the 100's of PPM in HC's for example. The limt is say a 100 or so. My car produces with cats in closed loop almost imperceptable HC's. I'd have to go find my smog report to get you some real numbers. 2) taking your cat out you will see that the donut slides over a flange that slips into the header collector so that you almost don't need a gasket. That part of the exhaust is so overbuilt you can seal it with aluminium foil! Your gaskets may look crappy but are sealing better than you think. Just take the cat off and shake it. I bet you dinner all kinds of crap rattles and comes out of there. Sorry my cats are punched. Also, There is a trick to getting the cat crap out. You can't just punch it.
Fatbillybob, well the cat seemed fine when I took it off on Tuesday... no rattle and no white crap coming out. Visual inspection did not show any abnormality... I'll go ahead and install another O2 sensor, get new gaskets and put it back together, then warm it up and drive. If it happens again I'll get a fuel injection diagnostics.
Reiner, My Memory things the gaskets are 2 1/8" donuts. You can get them from Sweeny muffler on Sepuveda/Normandie? for about 4 bucks each. You better measure to make sure. I guess I owe you dinner too... I don't think a bad o2 sensor can do it. When those things fail the car goes open loop and that is not too rich to cause a melt down. I still think you have a cat obstruction. There is a funny baffle in there and a bunch of stainless cloth wrap in there. You can only see part from one end. You should try my punched out cat to see if the problem recures. Also, if you get a pass on a smog machine you have no fuel or spark problem. That is a cheap diagnosis for about 40 bucks.
Boy does this bring back vivid memories !! Back when i had my 328 , the same thing happened to me.The warning light came on all of the sudden,and i was a mile from home. So i immediately turned around and drove home.I got the car in the garage and went to look underneath the rear and discovered the cat was a bright cherry red,and i do mean RED.I was amazed how fast the whole thing happened. The cause was a bad coil ,so the front bank of cyl.were not firing.I had these visions of the car and house becoming a smoking hole in the ground ! Replaced the coil and was good to go.
Glad your car (and you) did not go up in flames. CATS are just not worth the money! Take them off and put your regular muffler back on or do a combination of no cats and a Tubi muffler. The sound is incredible! All you'll need is a pair of Tubi "test pipes", which run only $200-$300. You can do a search to find out more info. Don't know what you've heard, but you should NOT have ANY "Check Engine" or any other warning lights show up on your dash without cats. This occurs when care is not taken in taking the cats off. The thermocouples (one for each cat) and oxygen sensors (one for each cat) are VERY sensitive; treat them with care. A warning light coming up on the dash after removing the cat usually means at least one of these sensors is on its way out. I removed my cats and didn't have a single warning light show up.
