A fter correcting a carbon monoxide problem, the leaner mixture will raise the combustion chamber temperatures, and may increase NOx emissions. Plan on performing NOx repairs as part of carbon monoxide repairs. This would include a verification of EGR operation as well as ignition timing and timing controls. You also may want to consider using an engine cleaning product to remove carbon in the combustion chamber. This lowers compression ratios and removes potential hot spots that may be igniting the mixture already.
F ailing vehicles for excessive NOx emissions creates a new challenge for Colorado technicians.
Take additional precautions to increase the odds of a successful repair. B ack to top . Perhaps the number one reason is improper repairs to the vehicle that have little or no effect on emissions results. In some cases, the vehicle has failed with higher readings than the initial test. A ccording to Bob Bentley and Tim Barnett, CDOR compliance inspectors responsible for issuing waivers, some technicians ignore basic symptoms and recommend that their customers spend hundreds of dollars on what turn out to be unnecessary repairs.