New cat exhaust stinks like fireworks

[candymancan]

I got a new magnaflow cat on my 90 my old cat was shattered into huge chunks and was rattling bad.. My cat model is 94016 and it says on their site its for all grand wagoneers from early 80s to 91.. Installed it a week or so ago and it stinks.. Sounds amazing though paired with my year old flowermaster super 44 muffler..

I for the first few days didnt have the airpump pipe hooked up to it but it still stank. But i decided to remove the cap and hook the air pump up to it because i read it helps with the reaction process and to keep it cooler.

Anyway for a week now its been smelling heavy of gunpowder or matches or fireworks.. Im guessing im smelling sulfur.. It isnt rotten eggs its litterally like 4th of july out of tailpipe.. The smell is annoying and i dont like having my windows down due to the exhaust creep at red lights.

Never had this smell with my old cat even with it busted up.. The only smell i had with old cat was just really heavy exhaust fumes that made a car salesman move away after talking to me for a few minutes lol..

The heavy exhaust smell is gone but its swapped for gunpowder lol.

Im reading mixed feelings thats its normal and will go away for a new cat.. To its not normal and its a bad cat.. Which i highely doubt lol.. Too im running rich... But i doubt im running rich.. my plugs are clean as whistle and the tailpipe is clean inside.. and the old cat was also very clean no soot. I dont blow any black smoke out of tailpipe.. Unless i pump gas too many times on start up lol.

[Cheapthrills]

Could you be running too lean?

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[tgreese]

Too rich is easy with a blown power valve diaphragm.

For a '90, the cat should be a 3-way, which reduces NOx, CO and hydrocarbons. Of these, the only one that should be detectable by smell is HC, I would think. CO is odorless and colorless, and NOx will make you cough and eyes burn in high concentrations, but it does not have a taste or smell IME. So I would look for running rich first. Running lean will lower HC and raise CO and NOx, which should not be detectable by smell.

Do you have air injection? Depending on the cat design, it may or may not need it. A surplus of O2 could theoretically retard NOx reduction a bit, but that's probably negligible. It can only help for reducing CO and HC.

Plus HC overload maybe produces a bunch of odd reactions that could have a wierd smell. Maybe. Again IME, a car with a cat should have a really sweet exhaust, resembling warm moist air.

[babywag]

My new Magnaflow CAT stunk BAD for couple weeks, I was about ready to cut it out and get a replacement, but the smell went away.
Mine was running perfect and passed smog with flying colors...so it was the CAT and not a tuning deal.

EDIT:
Neither of mine have the air pump or related bits. EFI install allows removal of all that useless junk.

[will e]

Maybe you should change your cat's diet so that it's exhaust doesn't stink so bad?

[candymancan]

Lol.. Well if babywag says his stunk bad.. Ill give it another week or two.. The smell isnt AS bad as it was day 1..

But it stunk before i hooked the air pump to it and after so i dont think the airpump is having any effect with or without..

It does smell sweetish.. but still has that gunpowder smell like you just lit off fireworks.. At least it smells better then my old broken one.. the exhaust on that made you choke lol

[Tatsadasayago]

I've installed quite a few aftermarket converters and most do reek for a bit. The best thing you can do is get out on the freeway and run steady for an hour or more. That's a sure way to 'burn in the cat'. If you get the sulphur-eggs smell, you're likely dumping too much HCs into the exhaust.

[candymancan]

Well ive driven it for a week straight now.. probly couple hundred miles.. Isnt gunpowder a sulfure smell ?? Doesnt smell like eggs but like fireworks.

What causes too much HC s ?

[Mustang Shooter]

Candyman,
Is your new cat in the stock location?
I don't know how far back they are originally, mine had already been hacked out and had a cobbled pipe system.
When I have built exhaust systems on our projects, I try to mount the cats just off of the manifold or header collector.
Maybe if its too far back, your not burning something completely.
Just throwing something at the wall.
Dan

[will e]

I had my cat replaced about 4 years ago and never remembered any kind of weird smell. My CO values went down to .01 so I pass emissions easy.

[candymancan]

Candyman,
Is your new cat in the stock location?
I don't know how far back they are originally, mine had already been hacked out and had a cobbled pipe system.
When I have built exhaust systems on our projects, I try to mount the cats just off of the manifold or header collector.
Maybe if its too far back, your not burning something completely.
Just throwing something at the wall.
Dan

Mine is litterally after the y pipe right above and 1 inch out from the cross member for the trans

[Tatsadasayago]

Candyman, HCs are partially burned hydrocarbons...ie; partially burned fuel. The GM pellet style cats were notorious for smelling like hard boiled eggs if the engine was running rich. I suggest you run the hell out of it so it gets nice and hot...then the stink will likely go away.

[candymancan]

Well the smell is finally going away.. not really there anymore. However now that its cold out and i turned on my heater i noticed at stop lights its blowing in exhaust into the cabin.. I however do not have exhaust leaks on the piping.. So why am i smelling exhaust being blown into the cabin.

Also does the heater blow air out of the cabin when you open the ventalation doors by your feet.. When standing still if i open the vents the heaters blower sound changes and it sounds like air is rushing out of those vents. and then the exhaust smell disapears

[SJTD]

The the heater inlet is up high in the cowl so it pulls in air from there and blows it inside.

You're just hearing the heater blower when you open the vent doors since the cowl supplies the vents too.

[babywag]

Well the smell is finally going away.. not really there anymore. However now that its cold out and i turned on my heater i noticed at stop lights its blowing in exhaust into the cabin.. I however do not have exhaust leaks on the piping.. So why am i smelling exhaust being blown into the cabin.

Also does the heater blow air out of the cabin when you open the ventalation doors by your feet.. When standing still if i open the vents the heaters blower sound changes and it sounds like air is rushing out of those vents. and then the exhaust smell disapears

If you smell exhaust you do have a leak somewhere, no other way for it to enter the cabin.
All the heater bits are in the engine compartment, it's pulling in exhaust from a leak somewhere.

[candymancan]

maybe its the manifolds ill check the piping again