Not sure really, but perhaps you do not have enough time on the screen to see the two you selected. If it's sequential port injection, then you would need to capture at least one complete engine cycle (2 crank revs) to be assured of getting them since each injector usually fires only once per engine cycle.
_________________
Tom Roberts
(The Picotologist) http://www.autonerdz.com
skype: autonerdz
THE PicoScope Automotive Authority
In North America
When you first start to capture events that you are not familiar with, it is a good idea to have lots of time on screen & make sure that you are not zoomed in by hitting the 100% button (in the zoom toolbar)
James Dillon mentioned the "helicopter view" on a course that I took when I first started scoping. He likened it to looking at an object held very close to your eye & trying to work out what you are looking at. When you hold the object at arms length then it becomes clear. The same applies to a waveform. Get used to manipulating the time base so that you can evaluate what is going on.