- Feb 19, 2007
- Perris, CA
Took the wife's car (1999 Cavalier, 2.2 w/208k miles) for a smog check today and it failed. NOX was high (1159 measured, limit is 746) on the 25mph test. What's so confusing to me is that it was 40 (well under the limit of 459) on the 15mph test. I have no idea what would cause a difference of over 1100 ppm between tests. The other two things they measured, HC and CO, were virtually undetectable. HC was 1 at 15mph and 0 at 25mph. CO was 0.02 at 15mph and 0.03 at 25mph. Engine RPM was 1800 at 15mph and 1700 at 25mph. CO2 was 14.5 both times (but there is no limit) and O2 was 0.04 and 0.06. I bought a can of "guaranteed to pass" and put it in the gas tank immediately after failing the test. We have a 200+ mile trip tomorrow, so that will have a chance to work its way through. When I got home tonight, I put some seafoam through the brake booster, poured some down each of the spark plug holes and let it sit, and misted some water through the brake booster as well. Any ideas on what would cause these weird results, passing by a lot at one speed but failing by a lot at another?