how to pass the emission test for grand marquis

Need more information, do you have a copy of the emission test stating what failed? Is the car stock, or has it been modified? High mileage?

Without more information I can give you some general guidance. Do a tune up and check to see if the catalytic converter is in good shape. A new cat can work wonders when trying to pass a smog check.

I pass the emission test and low miles.so why I didn't get reqluar tags?

I have low miles