Jotun Grunt

[Melwis]

If I have, say, 4 counters on Grunt and there is not a total of 8 cards in all GY's. Can I still remove a few cards and then when I can't pay more upkeeps Grunt dies or do you have to pay the cost for each counter right away? And if you can't you don't get to remove any cards at all?

Help appreciated!

[Nihil Credo]

Nope, it's all or nothing. Partial payments for cumulative upkeep are explicitly prohibited.

[YuanTi]

502.13a - Cumulative upkeep is a triggered ability that imposes an increasing cost on a permanent. "Cumulative upkeep [cost]" means "At the beginning of your upkeep, put an age counter on this permanent. Then you may pay [cost] for each age counter on it. If you don't, sacrifice it." If [cost] has choices associated with it, each choice is made separately for each age counter, then either the entire set of costs is paid, or none of them is paid. Partial payments aren't allowed. [CompRules 2007/09/07]

Emphasis relevant bit.