Misfire on 2,4,6,8 Cylinders only

[Nater]

I installed a Edge EVO HT programmer on my 2002 Tahoe about a month ago and ever since then I have been getting misfire counts on all even cylinders. I backed the programmer back of the truck and still getting the same thing. I have replaced plugs and wires. Anyone have some ideas? I have been told possibly O2 sensor, but I don't want to keep throwing parts at it. Ideas?

 

[BRUTUS_T_HOG]

Can you actually feel a misfire or is it just counting them?

 

[Nater]

I can sometimes feel it at idle only, usually after truck is warm. When I feel it is missing I will watch the misfire counts on my scan tool. It is pretty frustrating.

 

[russellshireman]

using your scan tool with the engine running, take a look at your short term fuel trims for each bank. they should both fluctuate within 10% of zero. also, look at your voltages at your upstream o2 sensors to make sure they are both moving around. a fixed voltage is a good sign of a failed sensor or an incredibly rich or lean condition. does your bank 2 converter rattle? can you hear an exhaust leak from the manifold area? check these out and we can go from there.