If the lifter is bad it does not pump up thus the pushrod could sit lower then normal.

If you take off valve cover and let engine idle and watch that each rocker is getting oil from the top of the pushrod that is getting oil from lifter.

You could just leave the coils hanging so sparkplugs are still getting spark.

I would do this when engine is not cold.

It might be a little messy as oil spraying but your only doing this for a couple of minutes.

Lifter could be just sticking and needing a oil based cleaner used