Had my 1991 Chevy Caprice (155,000 miles) undergo emissions testing today, for Texas vehicle inspection. Results:
High Speed Emission Results (25 MPH) Low Speed Emission Results (15mph)
Standard Reading Result Standard Reading Result HC (ppm): 95 317 FAIL 98 307 FAIL CO (%): 0.53 8.70 FAIL 0.54 8.40 FAIL CO2 (%): 9.3 9.5 O2 (%): 0.1 0.1 Nox (ppm): 645 197 PASS 711 211 PASS DILUTION: >6.0 18 PASS >6.0 17.9 PASS
It badly failed the HC and CO tests, but easily passed the Nox test. What is the likely culprit here?
Thanks!