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Discussion Starter · #1 ·
A little out of my league here guys. Got a '91 california non-turbo that has high NO. Everything else passed with flying colors. What I could find out on an internet search is probably high combustion temp. If that is the case, what could led to that? Tags are do in Nov and dont want any suprises.

EGR? Vacuum lines are good. Is it to lean? I'm not a very good trouble shooter.
 

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Possibly too lean mixture or sparkplug heat range too high.
 

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Discussion Starter · #3 ·
Thanks BHart. Didn't think of gap on plugs, but makes sense. I will check that. I'm still thinking lean mix, but wrong plugs and gaps would not help. Thanks again, gives me some things to work on.
 

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No, I mean the correct heat range for the plugs. Make sure the correct plugs are installed (and correctly gapped) but there are usually various heat ranges of plugs that can be used.

fyi:
NGK Spark Plugs USA
 

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Discussion Starter · #5 ·
Yes. Thank you for clarifying. I will check that. So, would the wrong heat range increase the temp that much? Or, is it more likely that combined with lean fuel mix causing is issue. I have all paperwork from previous owners, and NOx was always high since California started checking NOx.

It failed to smog test. About 10 years if I remember, Nox was over 3300ppm. It was fixed but no record or what. Then the previous owner replaced the computer for the fuel system control unit. It passed smog, but NOx passed by 2 points.
That's a brief history of my wagon. (f.y.i.)
I will check the plugs for sure. Thank you so much.
 

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Where I live we don't have smog checks, so I'm unfamiliar with the details. I have a friend who ran a Volvo dealer smog station down south said that each model was different. He did remark that certain models were better tested when still cold in order to get a pass and that ALL did better on a fresh oil change.

Check around and see who has had better results with 200 series Volvos in your area. No point in just paying for endless repairs.
 
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