problem....won't pass smog!

[mustangRich]

it runs great, doesn't hesitate, but it does idle a little funny between 800 - 850 almost like a slight miss.
before i went to smog it i did change the spark plugs
(set to correct gap) and replaced the Idile Air bypass,and cleaned the MAF.


also i have no egr because its a 91 but it has 2 Cats with 1 oxygen sensor. do i need new ones?

it failed the (ppm nox)

i get about 230-250 miles to the tank around town and 260-275.

please help

 

[Alec]

Was the truck warmed up when it was tested?

 

[mustangRich]

yeah it was warmed up.... i also put some good 91 octane gas in to help it out. what a waste that was


what does the PPM/NOX stand for ?

thansk

rich

 

[Alec]

too many parts per million of compounds of nitrogen.

Don't put in higher octane unless you can't stop the pinging, that probably hurt you.

You're either running too rich, O2 is bad, or cats are bad.

How badly did it fail?

 

[mustangRich]

i get the paperwork and post it later

 

[RickOTR]

The smog machine should have told you what was wrong with it. By Federal law they are suppose to give this information. I take my X to the diagnostics shop a few blocks from my house and have them run a systems check. That way, I can avoid this hassel when I go to get my smog checked.