I moved from NY to California this year and just tried to smog my 420 SEL with 560 motor and failed by a huge amount. Readings are:

HC (PPM)

idle: Max=120 measured= 455
2500 RPM Max=140 Measured= 125

CO (%)

idle: Max=1.00 measured= 9.99
2500 RPM Max=1.00 Measured= 1.80

Anyone have any idea as to what might cause such high readings? BTW, the engine runs great. Idles smooth, has no hesitation and has lots of power.

Thanks for your help.

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1988 420 SEL
1991 420 SEL with 560 motor
1993 Miata