I once had a misfire register on my '96 Plymouth Voyager (gasoline,
though, not diesel). The dealership thought it was due to an injection
problem and treated it as such. While they were at it, they changed
the spark plugs as a matter of course.

The problem seemed to be fixed but resurfaced after not too many more
miles. Rather than taking it back to the dealer, where they were
apparently clueless, I started asking around the the applicable
newsgroup. Turned out to be a secondary ignition system problem where
both the plugs and plug wires had to be changed at the same time.
Changing the plugs alone sorta fixed the problem for a time, which is
why it seemed like the dealership had done it's job but then the fault
recurred. I changed both and it has not had a problem since.

-- Christian

hiya we have had this problem for about a year now. we have a 2.9
manual sedona and it started doing this maybe once a fortnight. it got
worse about a few months back and one morning it wouldnt start well it
had to have a new diesel pump and after 7 and a half weeks and £2800
it was sorted and we expected the limp mode problem to be cured also
but after a few weeks it started again and a leaking coolant pipe at
the rear was found to be to blame. this was sorted but has not cured
the limp mode kicking in when ever it feels like. kia have never found
a fault using their machine. problem on going......... sorry but your
not alone.......its booked into a kis specialist in the new yr ill let
you know how we get on...