what would make a 2004 Buick lesabre idles smooth runs rough at 4000 rpm
could be a faulty coil or ECM.. what does the car do at 4000? stall or change how ir runs all together? Any different noises than before?
If I am correct, this car as well as most have rev limiters to avoid possible damage to the engine. The only way to get the rpms higher than 4000 is by driving the car.
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