failed nox on 1990 6000LE

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legs - 18 Oct 2006 18:15 GMT

new to forum. ya we just bought 90 6000LE w/ 104,300 from florida older
couple.
clean undercarriage an runs like a charm...no problemos. butbeen told no
emission test down south. SO guess what. it just failed its first Mass
emissions test. nox is 3.60 all others(HC,OC) ok. so put in new air
filter, O2 sensor, pvc, changed oil. have been gettin all kinda opinions
on what ta do next before 2nd test. mechanic that did inspection suggested
new O2 an thats it?!
an if have ta bring to state registered repair shops places want 150+ just
ta run diagnostic. dont have local trustworthy mechanic so any suggestions
on what to try an replace or/an do next before 2nd test would be
appreciated HELP !!!!!

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Weird - 18 Oct 2006 18:25 GMT

NOX is formed under high cylinder pressure and temperature. You need to
lower one or both. The EGR valve is designed to lower the temperature.
How is it functioing? Or, your mixture could be too lean, however, you
replaced the O2 sensor, which should have helped if that were the case.
You could have excessive carbon build up, raising cylinder pressure.
Try using a "Combustion Chamber" cleaner that removes carbon deposits.

Cheers,
Howard

> new to forum. ya we just bought 90 6000LE w/ 104,300 from florida older
> couple.
[quoted text clipped - 8 lines]
> on what to try an replace or/an do next before 2nd test would be
> appreciated HELP !!!!!

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Geoff Welsh - 19 Oct 2006 08:13 GMT

It'll cost far more replacing parts at random than to have the car
properly diagnosed and repaired.
GW

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