1999 silverado 1500 w/ 5.3. It just started running on 4 cylinders where the right bank 2,4,6,8 plugs are not firing. It started working again for about 50 miles and then back it to missing on the right side. I was showing the the downstream O2 sensors at 99% with the voltages running .1 to .9. All o2 sensors ohmed good except for 1. I replaced the 4 O2 sensors, plugs, and wires. I tried spraying around the top of the engine to check for leaks. I am looking for next steps. I may be looking into the ignition system, or just break down and take it to a shop.

 

Have you put it on a scan tool yet? Sounds like of like a grounding issue, assuming the coils are not bad. All four going out at once precluded that happening, however. Nevertheless, don't let this go on, as it will damage your catalytic converter.

 

You might consider verifying that there is not any loose connection in the wire that sends power to the coils on that bank..

It should come from the 15 amp injector B fuse in the under hood fuse panel and supply power to the coils on that bank.
Should be a pink wire.. Ground is supplied by black wire and is common to all coils on that bank.
Could also be an ECM problem.

 

I have 12v on the 15 amp fuses to the banks and 12v on the 10 amp fuse to the ECM. I have 12 volts on the pink wire to all 8 cylinders. The black wire has continuity to the coil ground and the black wires on all 8 cylinders. All fuses under the hood check for continuity and relays check out.
Next steps are the coil or ECM?

 

I think I got it. It was some partially mouse chewed wire where they were touching each other or the frame. Separated them and fixed em up. She's running alright, for now. It blew a bunch of smoke for a mile or so. I suppose it had a bunch of fuel sitting in the exhaust.