2000 Ford Ranger – engine replacement

Dear Doctor: I own a 2000 Ford Ranger pickup with the 4.0-liter 6-cylinder that had an engine replacement. The replacement engine had 75,000 miles. Since the engine was installed it has been using a quart of oil every 900 miles. There are no leaks or smoke emitting from the tail pipe. My mechanic checked the compression and vacuum system. He said there was one cylinder where the pressure was lower, but it shouldn’t be a problem. I just replaced the spark plugs and had 1 spark plug that was black with buildup. Do you have any suggestions? Chuck

Dear Chuck: First, the compression that was low in the cylinder should be checked to determine if it is a valve or piston ring problem. This is done by squirting a small amount of oil in the cylinder. If the compression goes up, then the problem is piston ring sealing. If there is no compression rise, then the problem is a poor sealing valve. The spark plug that was black with buildup is the cylinder with the problem. You can either try going up in the heat range on that 1 cylinder or using an anti-fouler on the spark plug. This is an alternative to major engine repair. Also have the mechanic check the PCV system operation to make sure it is operating.

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