# '86 300zx won't pass smog... Help!



## xxVERITASxx (Sep 13, 2009)

I'm in CA trying to get my '86 Z31 non-turbo M/T to pass smog.

So at 15mpg:

*Gas------Reading---Limit*
HC:--------155-------128
CO:-------0.80-------0.80
NOx:-----2593------1106

I'm sure it's the EGR (at least for the NOx) because we did the hand pump and ran the test and the NOx passed. Does this mean it's the entire EGR system or just the valve. I'm also wondering if any EGR Valve is interchangeable with the Z31. i.e. can a Z32 EGR Valve work? Can a Z31 Turbo EGR Valve work? Does transmission matter?

Input please and thank you!


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## jdg (Aug 27, 2009)

Take your EGR valve out, clean the heck out of it, the EGR pintle, the ports under it, double-triple check the leak rate on the diaphragm itself. EGR valve will cause the NOx (no EGR means higher combustion chamber temps, hence higher NOx emissions) and part of the excessive HC readings (not enough EGR for what is programmed, throws off the O2, ECU feeds more raw fuel), and might also account for the CO levels being right at the limit.
Transmission -shouldn't- matter unless your car has one of those vacuum solenoids that only actuate in a forward gear. Not sure about your particular vehicle though... And I would also guess that a Turbo EGR valve won't work only because of the difference in exhaust pressures between turbo and non-turbo.


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## xxVERITASxx (Sep 13, 2009)

So i took the EGR Valve out and dunked it in Chem Dip and totally jacked up the diaphragm :lame:. Now I need a new one. Anyone know where i can find a used Z31 non-turbo, manual transmission egr valve? 

Also, are the EGR valves specific to transmission and turbo/NA or not?

Thanks


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## jdg (Aug 27, 2009)

xxVERITASxx said:


> So i took the EGR Valve out and dunked it in Chem Dip and totally jacked up the diaphragm :lame:. Now I need a new one. Anyone know where i can find a used Z31 non-turbo, manual transmission egr valve?
> 
> Also, are the EGR valves specific to transmission and turbo/NA or not?
> 
> Thanks


I didn't say to dunk it in Chem Dip! Jeeze...a bit extreme dontcha think? When a wire brush on the pintle itself, and maybe a bit of scraping around the ports themselves...
Besides, if the Chem Dip ate the diaphragm seals up, then it was the EGR valve's time to go anyways. Only a matter of time before it blew out, and a short matter at that. Heck, they were most likely bad in the first place.


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