Low compression caused by leakage from exhaust valves can cause the check engine light to illuminate indicating an engine misfire. The cylinder head will need to be rebuilt by a qualified machine shop if possible. Please note that this problem will require careful diagnosis because misfires can also be caused by basic ignition components like spark plugs, coils, etc.
Problems for specific Mercury models:
Car problem reports
Problem with your car? See what our experts say or submit your own.
Repairpal verified Mercury problems
The spark plugs may become dislodged from the cylinder heads. A loud popping noise can be heard and a subsequent misfire experienced. The threads on the spark plug ports in the cylinder head(s) can become stripped or missing when the spark plug is dislodged. The threads in cylinder heads may be replaced using “Lock-N-Stitch” aluminum inserts. Our technicians tell us thread replacement is performed when the vehicle is out of base warranty. Vehicles under base warranty receive a new cylinder head.
An alternator pulley, of the incorrect size, installed at the factory can be the cause of drive belt failure and illumination of the battery light. The alternator pulley should be inspected and replaced as necessary if the drive belt brakes. When the new belt installed, it must be adjusted to the proper tension.
The Check Engine Light can illuminate with codes due to the lack of EGR (exhaust gas recirculation) flow caused by the intake manifold passage plugging up with carbon and oil. The EGR valve has to be removed and the passage cleaned thoroughly. Partial restriction of this passage can cause Smog test failures for the NOx emissions without causing a drivability symptom.
The synchronizer shaft for the camshaft position sensor can cause a loud squeak or chirping noise due to failure of the upper bushing. The noise may be erratic and is usually present when the engine is warm.
The intake manifold O-ring gaskets commonly leak, causing stalling and poor idle quality; the Check Engine Light will illuminate.
A spring in the seat belt buckle may wear or fail, causing the airbag light on the instrument panel to illuminate. Failed buckles will require replacement.
4wd vehicles may develop a squealing noise coming from the front wheels when driving below 30 mph. This is generally caused by dry excluder seals, lubricating the seals will commonly correct this concern.