When I had the timing belt replaced on my first Hyundai, a 92 Elantra, it
took the dealer three times to get it correct. After the first time it
didn't run right. When I took it back they tried to sell me an expensive
tune-up.  I told them I had just recently tuned it up and in either case it
was running right before they worked on it. After going around a few times,
they agreed to look at it.  They found screwed up timing and bent valve
stems.  When they called me to say it was ready to be picked up the second
time, I insisted that the service manage drive it to make sure it was fixed
correctly.  He called me back in an hour to tell me it would be a few days
more, It was screwed again.  They finally had to import an tech from another
dealer to do the work.  Of course I only paid the original bill.  Never did
find out why it was so difficult.
bill