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Mentok · 12-22-06, 05:49 PM

I too have failed NOX in California. I replaced the Cat, the EGR, cleand the EGR port, and replaced an O2 sensor. I use only 91 Octane fuel from 76 (pro-power) or Chevron (Techron). What other causes could there be for a NOX reading of over 1100ppm?

The guy who performed the test suggested that it was possible that if I had a blown headgasket (I have) that the result of shaving the head and replacing the gasket would cause a smaller headspace and therefor greater compression. This greater compression he said, would cause a hotter burn. As I understand it, a hotter burn is what causes higher NOX. Have any of you heard of this?

Has anyone who has blown a headgasket later passed the strict smog tests that California and other states require?

Mentok
93 Legend

12-22-06, 05:49 PM	#15 (permalink)
Mentok Registered User Join Date: Dec 2006 Location: San Jose, CA Posts: 1 Car 1: 93 Legend iTrader: (0)	Other possible causes for NOX failure? I too have failed NOX in California. I replaced the Cat, the EGR, cleand the EGR port, and replaced an O2 sensor. I use only 91 Octane fuel from 76 (pro-power) or Chevron (Techron). What other causes could there be for a NOX reading of over 1100ppm? The guy who performed the test suggested that it was possible that if I had a blown headgasket (I have) that the result of shaving the head and replacing the gasket would cause a smaller headspace and therefor greater compression. This greater compression he said, would cause a hotter burn. As I understand it, a hotter burn is what causes higher NOX. Have any of you heard of this? Has anyone who has blown a headgasket later passed the strict smog tests that California and other states require? Mentok 93 Legend