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

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2 answers 1 comment
maybe there is something else wrong with the cylinder
I agree, maybe compression, vacuum leak or you have an injector problem.
Have an injector balance test performed i bet # 4 is not going to pass!