I have a customer who has taken care of her 9 year old Camry well and is getting good service from it over the long haul. She recently found the check engine light on and noticed a miss from the engine. The term “miss” is often misunderstood, but refers to a situation when the engine runs on less than the number of cylinders it is equipped with. In this case, it meant one of her 6 cylinders was not firing at all. A “miss” can refer to a constant condition or an intermittent one – in this case it was constant. Even though her car had seen relatively regular care, it has high mileage (in excess of 160k miles) and was processing some oil past the rings that fouled one or more of the spark plugs. The term “fouled plug” refers to a spark plug which has gone electrically open or shorted, meaning it will not fire across its gap because the electricity has found a lesser resistant path around that gap or the electrical potential can’t fire across a gap too large. Plugs can be fouled by a number of contaminants. Some include antifreeze, oil or fuel. In this car’s case the plugs were fouled by oil. Oil shouldn’t be in the combustion chamber in a quantity that would cause fouling, but in the case of this car’s age, some oil is passing the piston rings designed to stop it, as a result of wear. It takes some time for the plugs to foul, so replacing the plugs, while not a permanent fix, will help for some time. In the mean time the car running on all 6 cylinders will save enough money to pay the bill in a short period of time.