It could be a variety of things. dirty air filter, worn out spark plugs, bad 02 sensor, clogged fump filter, or even dirty injectors.
Pin cone
An ABS fault.
bearning on front breaks burn out
No , ABS is the anti-lock brake system
Since the first model year of the Mercury Mountaineer is the 1997 model it would be ( r134a )
Check the main crank pulley.
rings or seals
Bearing in: Alternator? Water pump? A/C Compressor? Belt tensioner?
That would be the 4.6 liter engine, which takes six quarts. * of 5W-20 according to the 2003 Mercury Mountaineer Owner Guide
Vacuum leak in a/c door control system . Look for vacuum leak under the hood.
Check into the ABS pump or module ---- I would say the pump
On a 1997 Mercury Mountaineer : I assume the fuel filter would be in the same location as a 1997 Ford Explorer : ( underneath the Mountaineer , below the drivers door , mounted on the frame rail )