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- - HIGH NO on Smog (https://www.corvetteforums.com/forum/corvette-c4-forum-14/high-no-smog-3454/)

mikenann

10-09-2006 03:21 PM

HIGH NO on Smog

Hello Everyone

I got a 1987 that is failing California Smog. It is giving me a high NO (1558) reading at 15mph but a clean NO reading of 308 at the 25 mph measurment.
Any ideas?
Before I break down and take it to the DEALER!!!!!

Tanks
Mike

C3 Starship

10-09-2006 05:31 PM

RE: HIGH NO on Smog

Can you lean out your idle setting?

All2kool

10-09-2006 08:39 PM

RE: HIGH NO on Smog

Catalytic Converter I'm sure.

mech259

10-10-2006 09:49 AM

RE: HIGH NO on Smog

Check your smog pump diverter valve, make sure it is opening up downstream air under throttle. High NO readings mean unburnt fuel in downstream exhaust. Take off hose on check valve on exhaust to see if air is pumping under throttle, NOT at idle. If you have air at idle or not under throttle you have either a bad valve or the switch is bad on the valve, Also, check your vacuum source to valve. [8D]

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