Have you changed the air filter too?
For a 1999 Mercury Grand Marquis : ( the engine air filter is Motorcraft FA-1668 )
Yes.
no
have you ever changed the fuel filter ?
The cabin air filter, in your 2004 Mercury grand Marquis, is located behind the dashboard on the passenger side. The air filter is directly behind the glove compartment.
99 G/M has no filter.
No. A 2001 Jeep does not have a cabin filter.
That car doesn't have a cabin filter.
motorcraft 820 S
According to the 1998 Mercury Grand Marquis Owner Guide ( and one of Fords websites ) The ( Motorcraft FL-820-S ) engine oil filter is used
The 1997 Mercury Grand Marquis owners manual shows : ( Motorcraft FL-820S ) and fordparts.com shows : ( Motorcraft FL-820 ) for the engine oil filter
According to most aftermarket filter manufacturers and e-catalog data, it appears the 2001 Mercury Grand Marquis does not have a cabin air filter. Just to be sure, might be worth a call to the parts dept. of any Ford-Mercury dealer to verify.