Mercury Mystique Runs Bad and Dies – Computer Says Engine Is Lean

Reader Question I drive a 1996 Mercury Mystique 2.0L. It is suttering and sometimes
stalling on acceleration. It is worse on hot days, it’s also worse when the AC is on. The mechanic told me to get the PCM reflashed based on a TSB he found but that only made a very slight improvement. The engine code says my engine is running lean and disconnecting the Mass Air Flow sensor made the
condition worse not better. Any suggestions? Thanks Kelly

Kelly,

Howdy! What about the basics like the spark plugs, spark plug wires, distributor cap and ignition rotor…if it is equipped with them. Worn out spark plug wires can cause an engine misfire (the problem you describe) and set a lean code in the computer.

Spark plug wires are cheap to replace, and if they have more than 60,000 miles on them they should be replaced as maintenance anyway.

I would check the fuel pressure as well; you might have a weak fuel pump, or a dirty fuel filter.

Blessings,
Austin C. Davis