Failed NY emmisions...NOx 2.38..thoughts?

[JRKOUPE]

This is my second emmisions inspection on my 90 i...last yr she passed. I run MarkD chip and magnaflowcat , 2.5 " single set up, BAS intake........ all else is stock. All her numbers were very good except for NOx......2.38, and limit is 2.30. The trusted shop mentioned she might be running lean but he wasnt sure and had no time to pursue it. He also mentioned exhaust felt very hot, and maybe shes not getting enough fuel...... Im wondering if I should just put stock 173 back in and hope she passes.......any thoughts if its chip related or other possible repairs needed.......vaccuum leaks, etc. My research points to bad cat, valves need adjusting, need of tune up, lazy O2 sensor. She is up to snuff overall and these points shoud all be fine......maybe I could use plugs perhaps or even an O2 sensor. Car has 117k miles, w/ no record of O2 ever being done.......car runs fine.. My skill does not include any of this diagnostic insight. THANKS.

[aaron.j]

I would start with stock chip

[winstontj]

+1 for stock chip & replace the 02 sensor...

if all else fails run some unleaded AVGAS or put some denatured in there....

[JRKOUPE]

NOx...

Good advice.....Ill plug the stock chip back in.....




denatured?.......pls explain.



How often shoud we be replacing the 0 2 sensor?


........at 75 bucks its not that bad.

[FredK]

denatured = denatured alcohol = ethanol with a few percent methanol so it is not consumable by humans.

[JRKOUPE]

booze

I thought that....but was worried about making a fool of myself

[winstontj]

denatured alcohol burns hotter, sooner and cleaner. If you drain down the tank so there's only 2 or 3 gallons (of premium) left in the tank and then add a gallon of denatured it'll burn like a champ. Get the motor & exhaust system good & hot just before they do the test and then right after you pass fill the tank to dilute the alcohol. It's not good to run for long durations (months) but it'll make you pass....

[winstontj]

denatured thread

http://www.e30tech.com/forum/viewtopic.php?t=35636

[Dibo718]

did your car over heat? and did you keep it running?, the cat could be clogged due to the honeycomb piece inside melting due to temp rasing and then cooling causing it to reshape. a basic sign of this though is a red hot exhaust. im just basing this off of your shop telling you the exhaust is running hot

[JRKOUPE]

did your car over heat? and did you keep it running?, the cat could be clogged due to the honeycomb piece inside melting due to temp rasing and then cooling causing it to reshape. a basic sign of this though is a red hot exhaust. im just basing this off of your shop telling you the exhaust is running hot

no overheating..........


I plugged in stock chip...she passed test! Its also possible she failed because she wasnt fully warmed up and she had been sitting for months over winter(?).............but all is good now.......thanks!