California vehicle emissions check: Sub-par- or super-STAR?

This is the second installment of two in this series. As before, individual experiences may vary.

From the first installment, basically, what resulted from the STAR performance test where the initial vehicle emissions evaluation was conducted was that my motor vehicle failed to meet spec. At 15 miles per hour and at a revolutions-per-minute (RPM) rate of 1,562, the vehicle failed in the NOx (oxides of nitrogen) emissions category only. For all other test categories, no problems were found.

Well, today, I drove the car to the shop where the automobile mechanic who performs repairs on the vehicle, works. He advised taking the vehicle to another smog-testing facility to have the automobile smog tested, and that was what was decided.

To put things in context, in the test done initially, the NOx measurement was 521 parts per million (ppm) of air, again at 15 mph and at an RPM rate of 1,562. The maximum allowable NOx limit specified on the print-out is 430 ppm. So, at that speed and RPM the maximum limit for NOx was exceeded.

This time around, at 15 mph and at an RPM of 1,555, the NOx measured 414. Therefore, NOx was well within acceptable limits. As in the previous testing procedure, the vehicle passed in all other categories as well.

So, why the difference?

Could it be that the vehicle was thoroughly warmed up before being subjected to the test? Was there variability in the test equipment at the two different facilities used? Was there a calibrating error? Was it any two or all three of the above? Was it something else entirely? Question is: If this can happen regarding my car, then is the same type of thing occurring in other folks’ vehicles also?

Maybe more importantly, so say, if the reason behind the discrepancy was that the vehicle had not been warmed up sufficiently enough prior to being tested, if this was, in fact, the reason, then what this suggests is that until the vehicle sufficiently warms, it is putting out unacceptable levels of emissions – in this case NOx. If so, is this even permissible?

As I mentioned in the first installment, had I agreed to have the diagnostics performed by the initial facility I took the vehicle to for testing, that would have been a $90.00 charge. I decided not to go that route and instead have the person that does the repair work on my car look over the STAR smog check report. Suffice it to say, no diagnostics testing was required and therefore no engine repairs were necessary. This is the first time I can ever remember something on this order happening.

This concludes this SMOG test chronicle.

For further information on STAR testing, see: “California Smog Check Program gets upgrade with ‘STAR’” here.

– Alan Kandel