Signs of a dying Catalyic converter?
 

Ok so heres my problem. After a long drive 20mins+ driving i can smell this burning plastic smell coming from my car. Theres no smoke or anything just smells like burnt plastic. I recently got some LS2 yukon coils and the harness was touching the alternator, so i put some anti heat cloth in between, thinking it maybe like a wiring getting hot or melting ( checked everything seemed fine ), but i still smell some kind of melting plastic. Then i thought it might be my magnaflow exhaust, it gets hot at the back but hasn't yet melted my bumper and i had it on for over 3k miles so far. But i did notice i'd have to clean the tips every 3 days or so because it gets really dirty... Should i need to clean it this much? i use silicon metal polish. while bleeding my brakes i see this under my exhaust sysytem(look at picture below). i got this white residue/brown burnt stuff on the bottom of my catalyic converter. I showed my friend he said it maybe a plastic bag that got caught and melted away (explains the burning plastic smell). but, every once in awhile i'd get a CEL light, i'd drive it around see if it goes awhile, after filling up my car with gas and multiple restarts, the CEL would go away... happen three time already, (I thought maybe its just the gas cap that was loose). I'm not really sure whats going on but, I think it maybe the catalyic converter going bad... black tips every 3 days, white residue on cat, intermittent CEL. I don't drive my car too crazy or anything, but i do redline my car once a day, and i am using 20w-50 dino oil. Any thoughts anyone?

Dirty tips are normal.
Need to know the exact CEL.
Your CAT looks like a rack of BBQ Ribs. I would try something like oven cleaner, steel wool, putty knife.

(adding onto what Expo already covered)

Dirty exhaust tips is perfectly normal.
your CEL could be anything from a bad cat to misfires to a vaccuum leak. Next time it comes on, go get the code pulled.
White reside on cat = nothing. It looks like something plastic got caught on the cat and melted, most likely a plastic bag.


to answer your question, common symptoms of a failing cat:
- loss of power
- increased 'gasoline smell'
- cat can glow red hot after driving
- rattling / clunking sound at high rpm's
- CEL regarding Catalyst (forget the code #)

keep an eye on those wires and try to reorganize them in a manner so that they're clear of the alternator.
That could lead to issues down the road of a wire gets exposed.

i couldnt imagine driving my car around till the CEL goes away, several times. a CEL means that something is wrong with your car. whats the point of maintaing and modding the car if youre not going to listen when it asks you for help? maybe i love my car too much.

I don't entirely agree. For example, if you leave your gas cap too loose, you will get a CEL. Tighten your gas cap and drive for a while, or a few cycles, and it goes away. Why? because it recognized that the problem no longer exists...i.e., you addressed it. Also, take off your cat and put a midpipe on, you should have a CEL, and it will always be there until you put the cat on and drive several days (or get some other reason for blocking it). A CEL doesn't mean something is wrong, it means that computer thinks something is wrong.

WHAT the CEL is matters far more than whether or not the CEL is on.

I would say: "I can't see driving around with a CEL without knowing why"

Hopefully some day manufacturers will do away with dummy lights and instead of a CEL, your head unit will display the error and error code. Or at least both. "Tighten your gas cap", or "your motor is dying" or "your ignition needs to be upgraded" or "your cat is failing".

Not "I think something is wrong, please go to a dealer and pay $89 and have them tell you what is wrong".


But then, that's why the manufactures do it.

CEL disappeared again... was gonna take it to the dealer to see whats the CEL code. I talked to one of my friends, he says it maybe a faulty/failing 02 sensor, since its intermittent... Not sure but its gone, and car runs great, when it happens again i'll be sure to bring to dealer asap.

i think the cel code for the catalyzer/o2 sensor is P0139

Junirol: why go to the dealership? unless you're under warranty, it's going to cost you about $100 to get the code pulled.

Try to run your car in the upper RPM range for the next few days. if my guess is correct, your CEL will come back. (SSV issue)

or in some cases, its your gas cap not seating properly.


those "bbq rips/brownish/black stuff" on your CAT because you caught a plastic bag on the road, it got stuck to your cat. This is why you got that burning rubber smell. drive it out under rain, over a few puddles of water it will clean itself.

Get the code read ... any auto shop can do it ... and they can usually do it for free .... or you can get a reader yourself and do it .... something like this

http://www.actron.com/product_category.php?id=249

Even if it is not on your dash it should still be in your computer memory where you can pull it from "pending codes"

If you are going to mod an OBD2 car ... you need one of these

I've had a bag get stuck to the cat. Smells like burning plastic for awhile. Eventually it will burn off.

You could try running the car hard to get the cat nice and hot, then go through a drive thru carwash that does an underbody wash.

update on this, ever since i started putting performance parts on my car that random CEL never showed up. At least not the one i wasn't expecting, might have been some kind of vacuum leak.

Bad cat

going up hill with a problem, no power

had to start when warm