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It failed the HC test at 15 and 25 mph and the CO test at 15mph. I was wondering what I could do to fix this. I was going to start by cleaning the EGR system.
The readings were..
HC 129, limit is 69 at 15mph
HC 134, limit is 75 at 25mph
CO 0.33, limit is 0.28 at
Thanks
From what I remember, the EGR system is primarily for decreasing NOx emissions (because it lowers the combustion temperature), but I don't think it will hurt by cleaning it out.
Check your air filter and spark plugs, and PCV valve.
90 LS with 264,565 just went 1 out of 2 for it's State of Texas inspection.
At the first place it failed the 25mph NOx test by less than a 5% margin of error. My mechanics took it to another inspection site & it passed rather easily.
They did run a test on the EGR Vacuum Modulator valve assembly. Part #25870-50010 & recommend that it be replaced.