Bigpete123

Guys,

I'm almost sure that my catalytic converter is shot. My emissions are horrible, many mechanics have gone through it and tell my my mixture is correct. My exhaust smells very strong/rich.

I had a fairly bad misfire for quite some time for the first year of ownership, my car was burning oil before the head gasket and valve job. For a while there, it was fouling up plugs (but we think this problem has been resolved).

It bogs down under accelleration and has a hicup in the idle.

Mechanics have tested the hell out of everything and have said the only thing left that they can think of is the Cat. Although it has not been disconnected to see if the idle is still rough. The problem is that the rough idle and hesitation are severe sometimes and other times the car is smooth as silk.

So now to my question.

Have any of you installed aftermarket cats? If so, what brand? how do you like them?

Are there any considerations to make sure the O2 sensor and any other systems interact with an AM Cat correctly?

I don't want to pay $800+ for an OEM unit if I can get something of similar quality via aftermarket.

PS, I don't want a loud exhaust. I want it to be as quiet as possible. So I'm not looking for any performance gains at all.

Thanks!!

Saijin_Naib

I'd be interested to know what you find, I think I'm in the same boat with my CE. That or the muffler is totally shot, but my car is acting the same. Plus, its kinda loud right now.

mr300ce

Unless a cat is plugged up, it will NOT cause engine running problems. Period ! It is a bit like a sponge in the exhaust, to clean up the emmisions.

And you can find this out by going 80 mph on the freeway.....

Or reving the engine up in park. If the engine will rev to 5k rpm and hold it for 15 seconds, the cat is clear.

Sounds like you need to find a better mechanic.

Don't expect ANY engine running improvements when you waste $$$ on a cat.

Although, your cat is very likely bad due to the engine misfires. Misfires will KILL a cat pretty quick.

Wolf190

yea mr300ce pretty much nailed it. But just for the heck of it.... I put a magnaflo cat and flowmaster 50 series muffler on mine with 2.5" tubing. Obviously this is louder than you want to go but if you leave the stock muffler and the center resonator, replacing the cat should'nt have any effect on the sound. The shop I took my car to was able to install the "cat-back" and keep the stock O2 sensor because it is located just before the cat where the two exhaust manifolds join into one piece.

Bigpete123

Thanks for the replies.

Although from what I've been reading online, I'm now confused. It seems that there are varying degrees of a cat being "clogged". If it is completely clogged, the engine will die... so obviously my cat isn't completely clogged shut.

However, when it is partially clogged or constricted, it increases back pressure and can cause rough idles and loss of power at low speeds (both symptoms that I have). These are things I have read on a number of sites just searching around... So is it possible that I have a partially clogged cat?? I have taken my car to three different reputable indy mechanics and they all have run all the tests they know of and can't find anything wrong aside from the symptoms.

In addition, last time I took it in for emissions 2 years ago, I failed miserably. I mean not even in the ballpark. The only way I could get it to pass was to have the mixture adjusted so lean that I was hardly able to drive the car... obviously a bandaid.

Given all of the other things that have happened to my car over the last 3 or 4 years (bad mixture, burning oil, valve job needed, fould plugs, bad injectors), it really seems to make sense to me.

Wolf190

Given all of the other things that have happened to my car over the last 3 or 4 years (bad mixture, burning oil, valve job needed, fould plugs, bad injectors), it really seems to make sense to me.




idk man replacing that cat is sounding good to me right about now... I would just go for it if I was you. Is the one you have now the original? If so, it's not hard to imagine that it would be clogged over the last 15 years or so.

hineywineries

I also agree with mr300ce and especially the part about finding another mechanic. A simple engine vacuum test will tell cats are restricted or valve timing is retarted. You said you had a valve job. If you have a 90 coupe, you should have an M104 double bumpstick engine. Setting valve timing on one of those isn't easy.

By the way mr300ce where are you? are you in Borax, Furnace Creek, Stovepipe Wells or where?

mr300ce

Lancaster, the west side beginning of the vast desert to the east.

I also have a new magnaflow 2 1/2" cat. Stock mufflers. great flow thru the cat, and super quiet ride. I like it that way in this car.

On my Supra I have the same cat (2 1/2"), but with a 24" resonator, and a Magnaflow muffler. Loud, but not annoying. Its a fast sports car so the sound goes with it, but the 300ce is my 'sneaky' fast car.

JSe420

Going through some old catalytic converter threads and came across this one. Im hoping to get my exhaust done soon and I wanted to put a high flow cat in. My question is, in my 420 would I absolutley have to buy two cats or could i just do one with a double inlet. I plan on doing a high flow cat with a borla muffler that I already have.

JSe420

anyone?

Sherman321

I'll tell you that my old audi 90 quattro had a dual cat setup that was converted to a single cat setup. It lasted for about 2 years before it clogged solid, with about 8 months of spotty performance. The PO did it and I was stuck with the bill. So no, I don't think it's a good plan from my experience.

RBYCC

Look at the Magnaflow spun metal cat series.
There are many configurations and sizes.
The design is a knockoff of the more expensive Random Technology Cat.

I run two on my M103TT and gained 11HP on the dyno when replacing Merc OEM SL500 cats...

Not expensive, about $110.00