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Forum > Emissions Component > Question

1987 Volvo 240DL 2.3L automatic - Very high NOx. Has new CAT.

What do I do next! The car runs great no problems, went to smog it and it failed for NOX 15 mph nox 3767, 25mph 3460, checked for vacum leaks none this year car has no EGR, HC & CO were OK, went and payed $230 for new cat went to smog again and it failed again NOX went up 15mph nox 3948, 25 mph 3613, HC & CO were good, the car has 155,000 miles runs great no shakes no stalling. p.s. 02 sensor is good.
Answer:

The problem with your Volvo should be one of two things... either the engine is running very lean (this should be indicated by very low CO on your emission test report), or the engine has too high compression, possibly due to carbon build-up. We'd recommend a smog check repair station conduct a compression test first, and if that's ok, make sure the oxygen sensor is feeding the correct voltage to the emission computer, and the emission computer is adjusting the air/fuel mixture properly. posted by SmogTips Support

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