If the Check Engine Light illuminates, indicating a problem with the front oxygen sensor, but the sensor tests okay, reprogramming the engine's control computer should fix the problem. Then, the Check Engine Light will no longer falsely illuminate and the acceleration, particularly from a stopped position, will be smoother.
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Newest reported Hyundai XG350 problems
Prior to replacing the automatic transmission fluid (to improve shift quality), make sure that the transmission fluid level is correct. Also, make sure the computer that controls the transmission has the most up-to-date adaptive programming information. When servicing these transmissions be sure to use fluid approved by Hyundai.
A defective exhaust gas recirculation (EGR) switching valve may cause an intermittent rough or unstable idle engine.