Clogged catalytic converter?

[john d 81SC]

Just bought an '88 Carrera w/ 119,000 miles. I'm assuming the catalytic converter is clogged. Any way of checking, and if it is clogged, any way of cleaning it out? Eventually planning to go to a Euro pre-mufffler and sport exhaust, but in the meantime.... Thanks in advance!

[rusnak]

I have a lot more miles, and mine is not clogged yet, but then mine is driven all of the time. Generally if you're passing smog easily and getting decent gas mileage, you're probably ok. I think Wayne gave the pointer in his book: shine a really bright flashlight in one end, and you should see some light on the other side. I'm probably going to buy the "sport" aftermarket one due to the high price and backpressure of the stock factory one. Eventually the catalysts wear out. Overfilling the car with oil can ruin your cat too.

[wholberg]

What makes you think it's clogged? When the cat on my 78 SC clogged, the car would not rev over 3K rpm.

One way to check is to take the cat out and look in the inlet. if you cannot see through then it's clogged. From what I understand, cats fail in two ways, they either stop catalyzing and you fail emissions, or the innards collapse (like mine did) and cause a severe exhaust restriction.

[1985coupe]

If it's clogged you would know it -barely any power to move the car. As suggested here a flash-light might do the trick although I'd assume you'd have to remove the cat to flash a light through it and look at the other end (someone can correct me on this?).

[makaio]

If it is clogged and you want to gut it out:

Buy new gasket's, bolts, and nuts
Remove cat
through outlet side beat up the catalyst material with 1/2" pipe or other suitable solid object
empty contents into trash can
re-mount cat.

[Steve W]

A punched out cat will make the car run like a dog with poor throttle response. Better to tack weld a lightly perforated pipe in there with steel wool packing around it, or just install a bypass or euro style premuffler.

[FenderGuy]

Originally posted by Steve W
A punched out cat will make the car run like a dog with poor throttle response. Better to tack weld a lightly perforated pipe in there with steel wool packing around it, or just install a bypass or euro style premuffler.

Not to hijack the thread , so the hollow cat i bought will make my car car run like crap?

can anyone tell me if the HE are stainless I just got them today and they feel heavy


see link here
Exhaust: 84-89 stock complete For sale

[makaio]

Originally posted by Steve W
A punched out cat will make the car run like a dog with poor throttle response. Better to tack weld a lightly perforated pipe in there with steel wool packing around it, or just install a bypass or euro style premuffler.

I disagree. My 78 SC with hollowed cat ran fine, and had fine throttle response. When I put a Bursch test pipe on, it back-fired like Uncle Buck's brown Labomba.

[Steve W]

It backfired because the low/mid rpm part thottle region had less backpressure from the bypass pipe and thus ran leaner. Adding fuel there fixes that problem. The punched out cat retains the low rpm backpressure, and thus did not go lean enough to cause popping and backfiring.

[LM3929]

TO TEST the cat drill a hole in front of the cat and measure the back pressure

[1985coupe]

I like this idea LM3929 since you don't have to drop the cat for that test; so you'd drill a hole in the pipe (that you'd weld back I'd guess?) and connect a pressure gauge? or just judge by the smoke and sound : ? Any numbers on what the back-pressure should be on stock cat-exhaust configurations and their effect in terms of HP loss (and effectiveness ) ?

[LM3929]

I will check tomorrow but if my memory seves me more than 4 to 5 lbs and there is a problem.

most people just use a self tapping sheet meal screw to seal the hole.

[911quest]

If you have a itemp gun you can measure the temp of the cat measure both side of it inlet and outlet you will notice a significant difference if it is clogged

[creag44]

If your cat is clogged you dont wanna hollow it out. Cats are suppose to be made to be fail proof. If your cat fails that means that something is wrong, its almost like a derate for your car. I would check for any problems with the car and replace the cat or get the sport exhaust. To check for cat failure, your car will run like crap. You can remove it and try and look through it, use a pressure gauge, and the easiest I have seen so far and quickest is just use a temp gun and check for differences in the heat of the inlet and outlet. Hope this helps

-Mat

[swa911]

My cat clogs all the time.

Then it coughs up a hairball.

Sorry......I couldn't resist.