My '96 3.8L Camaro failed it's first California emission test. It's gotten near the maximum allowed before but that was a HC issue which wasn't an issue this time. This time it failed due to high NO numbers.
I don't have any CEL or any rotten smells coming from the car. Mods are an intake, headers, high-flow cat and exhaust system but I've had all those the past 2-3 checks and haven't seen numbers like this. The NO numbers were about half in the two previous emission checks.
Where to start? Plugs, wires, fuel filter, O2 sensors, etc are all under 2 years and less than 12k old. Cooling system just drained/refilled. The EGR valve, as I understand, might be a culprit and it's probably near 8 years old and 80k on it though again, no CEL.
What else would contribute to a doubling NO test count?
I don't have any CEL or any rotten smells coming from the car. Mods are an intake, headers, high-flow cat and exhaust system but I've had all those the past 2-3 checks and haven't seen numbers like this. The NO numbers were about half in the two previous emission checks.
Where to start? Plugs, wires, fuel filter, O2 sensors, etc are all under 2 years and less than 12k old. Cooling system just drained/refilled. The EGR valve, as I understand, might be a culprit and it's probably near 8 years old and 80k on it though again, no CEL.
What else would contribute to a doubling NO test count?