 I took home my 2006 Elantra the next day after 40 miles the check engine light came on.  I took it back to the dealer he said every thing was fine. I got 1/2 mile and the check engine light was on again. I see another review that has the same problem. I am wondering is this a problem.  They say I will get a new car tomorrow.  The code is cyl 4 missfire when they run a computer check. 