Emissions Test NOx-Need Catalytic Converter :(

Please help. 93 Oldsmobile Cutlass Ciera S.
Failed NOx emissions 2 times, same results different facilities, passed everything else flying colors. Told catalytic converter not cooling enough for me to pass but everything else working fine. No engine light on except Fuel Light always on. I seem to have the symptoms of failing converter...rough idle, bad milage etc. Today had oil change, fluid top up etc then had my second test. Also after the guy did my oil change I saw a little white slightly bluish smoke that was never there before but went away once the car warmed up.

I think I am going to get a new catalytic converter aftermarket at my used parts place for $75 and get my mechanic to install it then retest. :headshake Any Suggestions? New Converter?

Thanks,

Gokart



1st Test Results:
ASM2525
HC ppm- Limit 60 - My Reading 39 (PASS)
CO% - Limit 0.33- My Reading 0.11 (PASS)
NO ppm -Limit 450 -My Reading 790 (FAIL)
RPM 1390-VALID
Dilution: 15.0-VALID

Curb Idle Test:
HC ppm- Limit 200 - My Reading 84 (PASS)
CO% - Limit 1.00- My Reading 0.35 (PASS)
NO ppm -Limit N/A -My Reading N/A
RPM 665-VALID
Dilution: 14.9-VALID

-----------------------------------------------
2nd Test Results:
ASM2525
HC ppm- Limit 60 - My Reading 46 (PASS)
CO% - Limit 0.33- My Reading 0.17 (PASS)
NO ppm -Limit 450 -My Reading 773 (FAIL)
RPM 1404-VALID
Dilution: 14.8-VALID

Curb Idle Test:
HC ppm- Limit 200 - My Reading 58 (PASS)
CO% - Limit 1.00- My Reading 0.14 (PASS)
NO ppm -Limit N/A -My Reading N/A
RPM 678-VALID
Dilution: 14.8-VALID

Welcome to AF. No mention of engine, but the usual issue with nox is an inop egr system, if this is ok, then the cat is next, why get a used one could be as bad as yours.

Thanks for your reply maxwedge. I took your advice and replaced the cat with a brand new one instead of used and It still failed although when my mechanic sent it to be emissions test is was not warmed up at all.

When he added the gasline antifreeze to my 1/4 tank of gas and a few other tweaks it failed at 1133 at his associated emissions facility...after the cat change it went down and failed at 840. I am going to test it again tomorrow warm it up, add some gasline antifreeze and check it at one of the facilities I used earlier. Anyone have any ideas? Not quite sure what to do. Thanks.

Again what engine???

My Engine is 3.3L, V6