SMOG FAIL ON NO

1991 Isuzu Trooper

Tiny

mkelee@cox.net

February, 21, 2012 AT 12:47 AM

Would not pass smog I ended up replacing headgasket, valve job, valve lashcomplete tune up, all new vacuum lines and pcv, sensors ect. It still failed just barely, it failed NO
max is 704 @ 15 mph it measured 854
max is 606 @ 25 mph it measured 638
tech checked egr working fine
tech suggested changing timing from 13 degrees to 9 degrees
Any Ideas?

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3 Answers

Tiny

rasmataz

February, 21, 2012 AT 12:51 AM

Check the EGR valve, a problem with it will caused the Nox -oxides of nitrogen to go high due to excessive combustion temperature

Tiny

mkelee@cox.net

February, 21, 2012 AT 1:15 AM

The tech checked it out using a vacuum pump/gauge said it was working

Tiny

rasmataz

February, 21, 2012 AT 1:29 AM

Tell him check the catalytic converter, oxygen and coolant temperature sensors-

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