Catalytic converter question?
Thread Starter
Junior Member
Joined: Sep 2000
Posts: 18
Likes: 0
From: Portland, OR, USA
Catalytic converter question?
What is the stock type of catalytic converter for the 91 3.1L Firebirds? Is it a 2-way or 3-way converter...
Also is the Dynomax super converter better at cleaning emissions than the stock unit...
My car does not pass by 5 hundredths of a point on the NOx
My readings: 0.64 THC
3.05 NOx
4.00 CO
Their standard in Oregon: 1.20 THC
3.00 NOx
32.00 CO
KeithM
Also is the Dynomax super converter better at cleaning emissions than the stock unit...
My car does not pass by 5 hundredths of a point on the NOx
My readings: 0.64 THC
3.05 NOx
4.00 CO
Their standard in Oregon: 1.20 THC
3.00 NOx
32.00 CO
KeithM
Senior Member
Joined: Jul 2001
Posts: 904
Likes: 1
From: Modesto, CA USA
THC!?!?!? Wow!! You could get stoned off of your car!!!!!
Before you go replacing your cat check a few other samll things that don't cost so much. Here is a list of small crap that can cause you to fail.
1.) air filter, How old is it?
2.) O2 sensor, Has it ever been changed?
3.) Plugs, wires, cap and rotor. At lest check them.
4.) EGR valve. Check it to make sure it is functioning.
5.) Oil. Belive it or not if your car is waaaayyy over due for an oil changed it can increase your emission #'s.
Make sure you warm the car up really good before you get there. this will help make sure that the cat is at operating temp and will make it easier to pass. Just gun it from the stop light a couple of times, or do like I do I take my car to a test station accross town.
If you are worried that your cat is cloged you knock on it with your knucle. If it rattles it's clogged up.
To answer you question. No the aftermarket high flow cat's are no better then original. they are just less restrictive. All though the GM cat flows dam good.
Before you go replacing your cat check a few other samll things that don't cost so much. Here is a list of small crap that can cause you to fail.
1.) air filter, How old is it?
2.) O2 sensor, Has it ever been changed?
3.) Plugs, wires, cap and rotor. At lest check them.
4.) EGR valve. Check it to make sure it is functioning.
5.) Oil. Belive it or not if your car is waaaayyy over due for an oil changed it can increase your emission #'s.
Make sure you warm the car up really good before you get there. this will help make sure that the cat is at operating temp and will make it easier to pass. Just gun it from the stop light a couple of times, or do like I do I take my car to a test station accross town.
If you are worried that your cat is cloged you knock on it with your knucle. If it rattles it's clogged up.
To answer you question. No the aftermarket high flow cat's are no better then original. they are just less restrictive. All though the GM cat flows dam good.
Supreme Member
Joined: Sep 2000
Posts: 1,562
Likes: 0
From: Los Angeles, CA
Engine: LH0 3.1L
If you are just BARELY failing, you might want to just look for a quick fix. To lower high NOx:
-Check/replace air filter
-Back timing out a few degrees
-Check for vac. leaks
There's not much you can do to your EGR valve besides replace it.....and it ain't cheap. If it's defective it will cause high NOx. Although, if a EGR valve is fully non-op, the car will usually be a gross polluter.
-Check/replace air filter
-Back timing out a few degrees
-Check for vac. leaks
There's not much you can do to your EGR valve besides replace it.....and it ain't cheap. If it's defective it will cause high NOx. Although, if a EGR valve is fully non-op, the car will usually be a gross polluter.
Thread Starter
Junior Member
Joined: Sep 2000
Posts: 18
Likes: 0
From: Portland, OR, USA
The car was actually just from the dealer fixing it ( it used to be way off scale -- a bad lifter ) and they said they could not do anything more to get the emissions to lower.
The engine is a fresh rebuild ( overbored 0.20 over ) plus 900 miles.
The dealer had replaced the Dynomax cat that I had previously install saying that the cat was bad, but it still did not pass. Then they found the bad lifter. ( Probably was not a bad cat -- so I probably got robbed $700 )
The timing is already retarded by 4 degrees.
I put in new plugs, wires, cap, rotor, O2 sensor, a TPS, and I rebuilt the distributor.
Might putting a lower temp thermostat, ie. 170degree, and a manual fan switch lower the combustion temp enough to lower the NOx?
KeithM
The engine is a fresh rebuild ( overbored 0.20 over ) plus 900 miles.
The dealer had replaced the Dynomax cat that I had previously install saying that the cat was bad, but it still did not pass. Then they found the bad lifter. ( Probably was not a bad cat -- so I probably got robbed $700 )
The timing is already retarded by 4 degrees.
I put in new plugs, wires, cap, rotor, O2 sensor, a TPS, and I rebuilt the distributor.
Might putting a lower temp thermostat, ie. 170degree, and a manual fan switch lower the combustion temp enough to lower the NOx?
KeithM
Supreme Member
Joined: Jan 2001
Posts: 7,604
Likes: 1
From: ****SoCal, USA****
My fix for you.
Do you are you running the original factory coil?
REPLACE IT!
ANY HI-PO BRAND WILL DO.
ARE THEY THE 100% CORRECT SPARK PLUGS for your application?
Make SURE they are.
Meaning are you using a too hot or too cold plug for some type of "compensation"?
Fresh oil.
Fresh air cleaner.
Add two bottle so of Liquid Gumout to tank & use preminum Unleaded gas.
You'll pass.
You mean you didn't ask for the old parts back (your old CC)?
$700 for a CC?
Do you are you running the original factory coil?
REPLACE IT!
ANY HI-PO BRAND WILL DO.
ARE THEY THE 100% CORRECT SPARK PLUGS for your application?
Make SURE they are.
Meaning are you using a too hot or too cold plug for some type of "compensation"?
Fresh oil.
Fresh air cleaner.
Add two bottle so of Liquid Gumout to tank & use preminum Unleaded gas.
You'll pass.
You mean you didn't ask for the old parts back (your old CC)?
$700 for a CC?
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