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High NOx fails emissions but no codes - 1997 850 R

Help, Advice and DIY Tutorials on Volvo's P80 platform cars -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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abscate
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Re: High NOx fails emissions but no codes - 1997 850 R

Post by abscate »

Hide your spare change and used oil when Abscate visits…
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Post by matthew1 »

Pass :shock:


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1998 V70, no dash lights on

1997 850 T5 [gone] w/ MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace

2004 V70 R [gone]

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abscate
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Post by abscate »

Nice hot run before testing??

GReen
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Post by 454cid »

matthew1 wrote: 05 Feb 2026, 12:17 Pass :shock:



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Great to hear! Obviously the CO is good, but the others are approaching the limit.... is that about normal, or are they borderline? I'm not from an emissions testing state, so I don't have any idea what is typical.
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Post by scot850 »

That is great news! Was it a good burn out that fixed it?

Neil.
2006 V70 2.5T AWD Polestar tune
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Post by matthew1 »

454cid wrote: 05 Feb 2026, 14:40 Great to hear! Obviously the CO is good, but the others are approaching the limit.... is that about normal, or are they borderline? I'm not from an emissions testing state, so I don't have any idea what is typical.
I wish I had my OG 850 T-5 emissions printout for comparison. I looked for it in my posts here but I don't think I uploaded it. Short answer, I don't know.
scot850 wrote: 05 Feb 2026, 17:20 That is great news! Was it a good burn out that fixed it?

Neil.
Driving the cobwebs out of it around 3x per week for weeks, then rolling in hot to the testing station today. And fuel treatment... not Seafoam but a more grocery store brand like STP.
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1998 V70, no dash lights on

1997 850 T5 [gone] w/ MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace

2004 V70 R [gone]

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Post by scot850 »

I guess we should not question the Volvo Gods.........! :D

Neil.
2006 V70 2.5T AWD Polestar tune
2000 V70 R - still being an endless PITA
2006 XC70 - Our son now has this and still parked in our garage
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L - Sold
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - Sold

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Post by matthew1 »

I don’t. I didn’t make the rules, I just follow them, for instance MVS stickers aren’t likely to increase the chances of fixing a problem, but they can’t hurt.


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1998 V70, no dash lights on

1997 850 T5 [gone] w/ MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace

2004 V70 R [gone]

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Post by abscate »

I will guess you ran a bit richer on test2.

Note that you lifted HC from less than half spec to 3/4 spec

That lowered combustion temps which plummets NOx

Your cat cleaned up the HC so you still passed
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Post by volvolugnut »

"Driving the cobwebs out of it around 3x per week"

Fun repair work!

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