Need help with smog

CampbellSoup

Newbie
Joined
Mar 11, 2025
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I just bought this S52 M Coupe and I am failing smog in CA. I attached my most recent test. I have already done new air filter, oil and filter, changed spark plugs, cleaned MAF, ran catalytic converter cleaner and still failing. I tested for vacuum leaks and didn’t find any. Trying to avoid a $4000 catalytic converter. What else should I try?

Car has 172,000 miles and ignition coils, fuel injectors and one upstream O2 sensor is original as far as I can tell
IMG_7229.webp
. Car has 10.8% long-term fuel trim, but runs flawlessly. I don’t want to throw useless money at it. But also don’t want to spend $4000 if I don’t need to. Any ideas are appreciated. Thank you
 
Your CO is good, NOx ok, just high HC at the lower test point. High hydrocarbons result from unburnt fuel being measured in the exhaust stream. The good control of CO indicates that the primary emissions systems are operating well (O2/Catalyst) but high HC indicates problems with combustion. I would definitely look at getting the fuel injectors tested/cleaned and look for any problems with ignition coils. Good luck with getting it resolved.
 
I assume you drove around on the freeway for at least an hour before your test, ensuring your cat was as hot as hell?
 
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