Hi all,
       In addition to being very noisy when cold, can bad hydraulic valve
lifters suddenly cause a serious loss of power while driving on the freeway
at 65 mph? They were pumped-up with no noise whatsoever when I left home,
but once this happened, then they became very noisy and sometimes the van
didn't even want to move from the stop sign (Embarassment!). Does this mean
the heads will have to come off? I have already tried Marvel Mystery Oil and
ATF in an attempt to make them quieter.

Any help would be appreciated.

Sam