96 suburban won't start

Sounds like my 99 suburban. Would not start when air temp was low in the morning (60degF). Starter would crank but no other signs of life. As day warmed up, it would start and run fine. If you stayed at it long enough, on a cool morning, it might start, but run very ragged, as if only 3 or 4 cylinders were firing. If you could keep it running until engine warmed up it would get progressively better until it ran perfectly. To mechanic. Computer showed no codes except cylinder misfire when running rough. They prescribed cleaning the injectors and declared it fixed. Next morning same problems!!! Back to mechanic where they replaced the entire fuel injection spider assembly, with a used one from a wrecked car. We have had the car back one week and it runs perfectly even one morning that was 50 degrees. Mechanic says he had seen this before and had to do the same thing. Still sounds very hoakey to me that an injector will suddenly stop working at certain temps. However the two cylinders that were showing misfire on the computer look different on the injection tips. They look copper colored as opposed to all the others that are silver colored. Still no idea why all cylinders would appear to be dead at once at certain temps. Hope the used one continues to work well, mechanic said a new one is very expensive. Still waiting the final bill. I am not impressed with chevy on this one. mechanic says they ran this type injector 96?- 2000 and had some probs so discontinued using it.

Sounds like my 99 suburban. Would not start when air temp was low in the morning (60degF). Starter would crank but no other signs of life. As day warmed up, it would start and run fine. If you stayed at it long enough, on a cool morning, it might start, but run very ragged, as if only 3 or 4 cylinders were firing. If you could keep it running until engine warmed up it would get progressively better until it ran perfectly. To mechanic. Computer showed no codes except cylinder misfire when running rough. They prescribed cleaning the injectors and declared it fixed. Next morning same problems!!! Back to mechanic where they replaced the entire fuel injection spider assembly, with a used one from a wrecked car. We have had the car back one week and it runs perfectly even one morning that was 50 degrees. Mechanic says he had seen this before and had to do the same thing. Still sounds very hoakey to me that an injector will suddenly stop working at certain temps. However the two cylinders that were showing misfire on the computer look different on the injection tips. They look copper colored as opposed to all the others that are silver colored. Still no idea why all cylinders would appear to be dead at once at certain temps. Hope the used one continues to work well, mechanic said a new one is very expensive. Still waiting the final bill. I am not impressed with chevy on this one. mechanic says they ran this type injector 96?- 2000 and had some probs so discontinued using it.

The injector system on that truck uses a "poppet" tip on the end of an electronic injector.
The ball inside the poppet will stick to the seat and cause a variety of strange starting problems.
To properly clean the injectors on these trucks (and everyone listen closely)
YOU CAN NOT CLEAN THESE INJECTORS AND UNSTICK THE POPPETS WITH CONVENTIONAL CLEANERS OR CLEANING METHODS!!!!!!

To properly unstick the poppets, you need to inject high pressure nitrogen into the injector to force the ball of the seat and past the dirt buildup, then follow it with a cleaning solution of gas and 5-10 TEC.
If the poppet will not unstick with this procedure, then replacing the injector system with an updated one will eliminate the problem