How to Install the Crankshaft Sensor on a 1998 Grand Marquis

The 1998 Mercury Grand Marquis came standard with a 4.6-liter V-8 and a four-speed automatic transmission. Your 4.8-liter engine has a crankshaft position sensor that relays the rotational position of the crankshaft so the computer can synchronize the ignition timing. A faulty crankshaft position sensor can cause sluggish performance, and can even prevent your engine from starting all together. Your crankshaft position sensor is located on the lower right side of the engine next to the air conditioning compressor, which has to be removed to gain access to the sensor.

Instructions

Removal

1

Park the vehicle on a level surface and set the parking brake. Lift the vehicle hood and support it with the hood prop rod. Lift the front of the vehicle into the air with a floor jack and place jack stands under the front frame rails. Lower the floor jack until the vehicle rests securely on the jack stands.

2

Draw out a sketch of the serpentine belt routing with a pen and paper and set it aside. Place the square head of a breaker bar into the square hole on the tensioner arm. Rotate the belt tensioner counterclockwise and remove the belt from the alternator pulley. Slowly release the tensioner to its natural resting position and remove the serpentine belt from the engine.

3

Position yourself under the vehicle and remove the six screws securing the splash guard under the vehicle. Remove the splash guard. Locate the air conditioning compressor and crankshaft position sensor on the bottom right hand side of the engine. Disconnect vehicle wiring harness from the compressor and crank position sensor.

4

Pry the wiring harness retainer from the side bracket of the air conditioning compressor with the flat-head screwdriver. Loosen the three bolts securing the air conditioning compressor to the engine with a socket and ratchet, but do not remove them. Wrap the mechanics wire around the base of the compressor and the exhaust manifold so the compressor will be supported when removed.

5

Remove the compressor bolts by hand and allow the compressor to hang to the side from the exhaust manifold. Do not remove or bend the air conditioning lines in any way. Remove the crankshaft position sensor mounting bolt with a socket and ratchet. Pull the crank position sensor from the timing cover slowly.

Installation

6

Compare the new crankshaft position sensor to the old and make sure they are the exact same. Coat the O-ring at the base of the sensor with fresh engine oil and slide the sensor into the timing cover. Line up the bolt hole with the mounting hole in the timing cover and install the mounting bolt. Tighten the position sensor mounting bolt to 71 to 106 inch-pounds with a torque wrench.

7

Swing the air conditioning compressor into place and loosely install the three mounting bolts. Remove the mechanics wire from the compressor and exhaust manifold. Tighten the compressor mounting bolts to 24 foot-pounds. Press the wiring harness retainer into its mounting hole on the compressor bracket. Connect the wiring harness to the compressor and crank position sensor. Lift the engine splash guard into place and install the six retaining screws. Tighten the screw snug with a Phillips head screwdriver.

8

Lift the front of the vehicle off of the jack stands with a floor jack. Remove the jack stands and lower the vehicle to the ground. Remove the floor jack. Inspect the serpentine belt for any major cracks, glazing or other damage and replace as necessary.

9

Route the belt around the engine pulleys using the sketch made earlier as a reference; hold the belt tight by hand at the alternator pulley. Place the square head of the breaker bar into the square hole on the tensioner arm. Rotate the tensioner counterclockwise and slip the belt over the alternator pulley. Slowly release the tensioner arm and remove the breaker bar. Shut the vehicle hood.