2000 Elantra with 138,000 miles has developed a hesitation when first accelerating. The hesitation is more noticeable under hard acceleration. There is also an intermittent miss at low speeds. Engine runs strong with no miss at RPMs above 2500. There is no check engine light. Have replaced plugs and wires with NGK. Throttle Positioning Sensor (TPS) replaced but didn't help. Coil pack checked over and has no carbon tracks or cracks. Dealer recently replaced purge control valve (emission control). Fuel filter was replaced 20K ago. Would appreciate any suggestions.

OK. so I see everyone really scratching their heads on this one :screwy:. Turns out the problem for the most part is due to a bad fuel injector pressure regulator. I say for the most part, because while it is a huge improvement, the car still stumbles or hesitates before revving up if the accelerator is punched hard from standstill. Thanks to Elanor96 on hyundai-forums.com for her post that led me in the right direction. Would still love to know why the hesitation, so if anyone would like to hazard a guess...