I am posting this for a friend. He has a 2003 4 cyl auto Elantra. His problem is strange, while driving the car is normal for maybe 1 - 5 hours then out of nowhere the car will only go 15-35mph and no matter how much you press the gas pedal the car will not accelerate. It is a bogged down loss of power not like it's just stuck in a low gear. This has been happening for a while now but now it's happening all the time and very frequently. Before he could shut the car off for 5 minutes and it would be ok for another 1-5 hours. It got so bad that he can only go 20 miles before it happens and now it seems the longer he lets the car sit off the longer he can go before the problem happens. Any thoughts? Hyundai has had the car for a week and still have no clue what the problem is but it has not happened while they have had it. They had the car Towed from Reno NV. to Near Sacramento CA. for fear of driving it in the mountains like that. There is no CEL or any stored codes which is making this really hard.