My 2011 Lincoln Town Car. Has a very rough idle that comes and goes. The computer does not show any codes when this happens. The car has new spark plugs new fuel injectors new coil packs. The strange thing is when I was unplugging one coil pack at a time to see if there was a change in the way the engine ran. once there was an engine code present in the computer the car ran better. This problem has me quite confused. I have checked all the vacuum and the intake and the problem still exists.
What makes this problem better or worse?
When I cause an engine code it runs better.
How long has your 2011 Lincoln Town Car had this problem?
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Very odd that it's not setting a code. This could be a vacuum leak too. Sometimes you can get a vacuum leak when the engine is cold and as it warms up and things expand, it goes away. I'd check for leaks with a cold engine.
Also check fuel pressure.
Alex
