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just failed emission with too much NO.
would a clogged converter cause the car to stumble and jerk? and slow acceleration? those jerk and spongy gas is happening most at 2k rpm range.... or at first or second gear.

how much is it typically to replace the converter?
thinking it's about time to throw it away. things keep breaking down.

I would not immediately suspect the cat. Given your description of symptoms I would check the air intake hose for cracks. Also check the spark plugs and if in any doubt, replace.

I have to emissions test two cars, one my mx-3 and it has been an interesting experience here in Ontario where the tests are mandated and very very very inconsistent. I have yet to see anyone warm up a vehicle before performing the test

I am trying to get my MX-3 to pass. It failed the first attempt today but only on HC driving test. It probably is just an effect of not really being warmed up. I think driving it on the highway at WOT will clear it out.
It has a newish Cat and O2 sensors - about 10,000 miles on them, and I changed the plugs and sealed up a couple of hairline cracks on my intake hose. That addressed my stumbling while accelerating in low gears. The plugs sooooo needed replacing. It only took me 20 minutes and 25 bucks in parts.

On my Porsche I got inconsistent results and silly or no diagnostics. My Porsche passed the driving test in all areas but failed only the CO at idle when the technician complained about inconsistent idle speed. The tech's comments : "your car needs a lot of work." When pressed he suggested the cat must be bad. I know the cat is fine.

I had to take it back twice after making adjustments to idle Fuel/Air mix and idle speed, so I have paid for three tests just to basically compensate for the lack of someone figuring out that a reading that only affected CO at idle might be related to the idle. Needless to say I would have been pissed to have paid to replace the cat... and still failed. And then to discover that 3 minutes with a hex wrench and a slot head screwdriver would have fixed it.

I just wish there were more places where you could drive it in warm and get it tested right away, but the mandatory price limits here probably preclude that. I would gladly pay more for an iron clad appointment so I could drive the car up with the cat cooking.

plugs are new, and i don't seems to find the hose to have any cracks.
i do have a bad O2 sensor... and it's surging after i drive for a while.

wonder if i should replace O2 first or converter first, just want to spent nothing to get it to run ok.

Cats can be tested. They drill a hole infront of it hook it up to the machine and get the readings before the cat and after and see how it preforms.
i dont know how much it would cost probly lot less than a new cat

You can buy a Magnaflow cat on Ebay for $50-80. Then it''l cost you about $50(depending on where you take it) to put it in.

Did you fail at a certain RPM, or all RPM?

FYI, the O2 sensor isn't used during idle .... so if you failed idle, replacing O2 won't help you there.

2fazed wrote:You can buy a Magnaflow cat on Ebay for $50-80. Then it''l cost you about $50(depending on where you take it) to put it in.

Would those $50-80 cats actually work tho?

lakersfan1 wrote:Did you fail at a certain RPM, or all RPM?

FYI, the O2 sensor isn't used during idle .... so if you failed idle, replacing O2 won't help you there.

it failed both the 25/25 and 50/15 test.

Do places test idle readings? Here in Cali it's just the 15mph and 25mph test. Both readings for me were at around 1500-1600rpm. First time I failed ( CO at 0%, NO at twice the legal ), changed out the O2 and I passed with numbers that were close to the state average. I would definitely change the O2 and retest the car before trying to replace the cat.

i just failed my emissions test today as well, excessive readings on HC and NO. the HC reading wasn't far above legal, but the NO readings were double the limit.

my friend is manager of a Firestone and is having the car checked out for me, hoping this means a free diagnostic analysis. so far, everyone (emission inspector and techs) has speculated that i need to replace the cat.

at the moment i'm cleaning my air filter and checking the plugs. i'll try to determine if there are any bad vacuum lines, then i think i'll swing my the parts store and pick up an O2 sensor. finally i'll run a seafoam treatment to clean up the injectors and reset the ECU.

i'll let you guys know if this works out....and if it doesn't i guess i'll order in a new cat.

Juans_93_MX3 wrote:

2fazed wrote:You can buy a Magnaflow cat on Ebay for $50-80. Then it''l cost you about $50(depending on where you take it) to put it in.

Would those $50-80 cats actually work tho?

I passed Illinois emissions and Nevada emissions with a Magnaflow cat.