my grand marquis 2005 one side is lower then other side

One side lower than the other, is this on the front of the vehicle or the back? Also front or rear did you change the coil springs. Is there a air spring in the rear?

Shocks alone, do not have ANY control of ride height. Struts do because the have a spring around them. You may have a bad rear air spring (air bag), broken air line or bad air spring solenoid on the rear.

i changed coil spring and shock rear and front... rear left side is down

About the only thing it could be is a bad spring cup, or the frame is bent.

Or a bad air spring, or air spring solenoid if equipped with rear air suspension.

Bob is 100% correct my 96 Grand Marquis had thr same thing