04 Rondezvous lifter problem.

[Blue Bowtie]

Welcome Aboard!

If a rocker stud has pulled, it should be pretty apparent when the cover is removed (see photo above).

If a lifter is not pumping up and adjusting lash, diagnosis may be more difficult. You can GENTLY try to verify the rocker bolts are not loosening, but keep in mind the torque specification for rocker bolts on most of these Chevy V-6 engines is only 18 ft/lb. Avoid over-tightening as this may strip the threads in the head, and that would require a lot more work to repair.

You may also be able to start the engine with a rocker cover removed and listen closely to each rocker to identify the offending cylinder(s). It could get messy with oil slinging around, but it can be done.