Piston failures in late-model engines are relatively uncommon thanks to computerized engine controls that keep a close watch on the air/fuel mixture, and knock sensors that back off spark timing advance if detonation is detected. Pistons are also lasting longer because many engines now come factory-equipped with stronger hypereutectic alloy pistons that can withstand higher operating temperatures, or even forged pistons. Some pistons also have a factory anti-scuff coating on the skirt to prevent damage if the engine overheats or runs low on oil.

Yet in spite of these things, pistons do sometimes fail. The symptoms of a piston failure can include engine noise (rattling or knocking noises while the engine is idling), oil burning, misfiring and loss of power.

If the Check Engine light is on and you find a misfire code for a specific cylinder, and the engine is suffering any or all of the above symptoms, it may be a clue that you're dealing with a mechanical problem rather than a fuel or ignition problem. Misfires can be caused by a variety of problems, including a dirty or dead fuel injector, a bad spark plug or plug wire, or a bad ignition coil on a coil-on-plug or multi-coil distributorless ignition system. But a fuel or ignition problem won't cause engine noise or blue smoke in the exhaust.

Loss of compression also can cause a misfire and a loss of power. A compression loss can occur if the engine has a burned exhau...