what is causing cylinder not to fire on 2007 GMC Yukon XL 1500

# 4 cylinder not firing changed plug and wires coil pack is firing cylinder is still missing

Asked by for the 2007 GMC Yukon XL 1500
maybe there is something else wrong with the cylinder
I agree, maybe compression, vacuum leak or you have an injector problem.
1 more answer
Have an injector balance test performed i bet # 4 is not going to pass!