1994 Isuzu Trooper adjusting the timing

it's controlled by ecm and non adjustable.

OH, that is very disappointing! so if I understand what you're saying....I was very careful to align marks as I put the new belt on and as careful as I could be not to move anything and apparently something is just slightly off and the only way to adjust this is to take the whole thing apart again and try again to hit the marks exactly without moving anything and after it's all back together hope it stays in the exact right position?

are you talking about the cam timing? that is different pay particular attention to pics as one is for single overhead cam and others are for dual cam