Here is one possibility: http://www.jcwhitney.com/autoparts/Product/tf-VehicleBrowse/s-10101/Pr-p_Product.CATENTRY_ID:2008663/showCustom-0/p-2008663/N-200728952+111+1985+600003813/c-10101
It's under the hood on the passenger side in a black box behind the battery.
On the left side of the steering column there is a light black tab that you pull down.
Mine was under the trunk lid. When you open the trunk you can see it up underneath towards the back. A white sticker with 5 black numbers on it. '94 Grand Marquis
removable panel under the steering column, there's two big black screws that come out
I believe the wiper module is built in the black cover that snaps on the wiper motor I believe .
That's how they work! There's a sensor on the front part of your dashboard. It'll look like a little black bump.
The Maf is down stream of the air cleaner lid its a black color box with a silver color tube.
The fuse box is under the dash on the driver's side. It is need the emergency brake, it should have a black cover on it. You have to kneel down to find it.
I just had a throttle position sensor installed in my 1999 mercury grand marquis. I feel certain it is located in the same place on your 1998. Look up top behind the air intake tube (large hose) leading to your throttle body. It is a rather small black hard plastic item. www.autoclinix.com is a good website for printing out the directions for installing all parts on your mercury grand marquis. Good Luck, Ms. Lena
Pull-A-Part Passanger side, against the firewall...big huge black box
Look under the trunk. It should be (possibly 2) a black plastic box. It (they) may inside a metal bracket and have a broken hose from backing up into a curb.
The thermostat gasket for a 1990 Mercury Grand Marquis is the standard "paper" type gasket, and a good RTV silicone is recommended. Permatex makes a sealant well-suited for the purpose - it's called "Water Pump and Thermostat Housing Sealant". You can also use similar sealants, such as Permatex Ultra Grey, Ultra Blue, or Ultra Black.