Odds are the stumbling is air in the fuel - pulled in at the heater plug, so to check pull the plug - if it has fuel coming out - it's not supposed to, the fuel's supposed to stay in - you have bumper to bumper warranty until 36,000 so tell the dealer to fix it
they'll put in a new head - which may or may not help - then after the warranty expires - start looking for Racor fuel heads.
- this is the thread on the fuel heater plug - there are several others about air in the fuel.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=24616
as to the shift - 4th is a stepping stone to 5 - it only stays there if you're going about 55-60 not fast enough to hit 5th. if you hit the overdrive off - both 4th and 5th are overdrive so they both turn off (although that will allow a lockup in 3rd - which doesn't normally happen)
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2005 CRD
stuffSkeptic quod gratis asseritur, gratis negatur