Hi
I am fixing up a 1986 Pontiac Firebird TA V8 carburetor manual transmission. I took it to get a smog test In California and it failed smog with evap and high HC failure. I replaced the defective evap parts changed the plugs and wires cap rotor and coil. Took for a second test now the report says high hc and no high way high like double the previous highs . But the Evap passed. Don’t know if it is a bad carb or cat or ? Any help would be great Thanks
- Leave California
Once I retire
Could well need the carb overhauled especially if it hasn't been done for a few decades. It's probably a feedback carb - if so the O2 sensor may be bad. Make sure the miles of vacuum hoses and gadgetry typical of 1980s carbureted cars are in good shape and hooked up correctly.
I will check the O2 sensors didn’t think of that
Don’t know if it is a bad carb or cat
Could be either.
Rich mixture and failed cat can both cause high HCs.
I imagine it's going to be pretty difficult to pass smog with a carburetted engine. It would have to be tuned very precisely. I would start with that. Without O2 sensors it's going to be pretty difficult to assess the condition of the cats.
