Question about Lincoln Mark VII
Sounds like an oxygen sensor problem. O2 sensors have to be warmed up to around 900 degrees to properly operate, so until they're up to temperature, the ECU ignores them and fuels the engine on preprogrammed fueling maps stored in the ECU. Once they're up to operating temperature, they provide feedback to the computer for properly fueling the engine. Blowing black smoke indicates a rich condition (excessive fuel), which usually is the result when and oxygen sensor is defective. The computer realizes the O2 sensor isn't working right and goes to a rich-fueling map for the engine. Rich running is not damaging, other than it can foul spark plugs and (if untreated for a long enough period) could clog the catalytic converter. This is better than a lean condition (too little fuel) which superheats the cylinders and causes them to detonate, which can fatally damage the engine. I would change out the primary oxygen sensors and see if your problems go away. You may need to get new spark plugs as well, especially if this has been going on for awhile - they may be carbon-covered and not firing efficiently.
Posted on Jul 27, 2008
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Posted on Jan 02, 2017
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