Why, 343 would you made the skull on mission 4 the silent cartographer inaccessible I have spent a lot of time trying to do the GRENADE JUMP it just doesn't work .IT'S REALLY PISSING ME OFF !!!!!!
I recommend you to switch to the old graphics while performing the jump, so you can have a better view of the landing zone. Try with plasma nades a few times, so you'll get used to the timing of the jump.
If you can't perform it, here's a simple way to get it.
Yeah, that skull it's a Little bit tricky, but don't give up!
The Warthog flip method is way easier than the grenade jump