can some one explain fuel trim to me

Did a search and nothing informative came up. I"m in the process of trying to figure out a very weird missfire when the engine is cold, and yes I have already checked the basics like plugs, wires, compression, fuel, ect. I have access to a scaner and learning obd missfier diagnosis but this is just a lil bit beyon my knoweldge at the moment and need a lil help. At the moment I want to see if its a lean missfire or a rich missfire but I don't know what the numbers mean or how to interpret them. So if someone could point me to a website or could post what you know about fuel trim what the numbers mean and how to interpret them I would be greatly in your debt.

Thanks
Gary

I have an online guide to scanner data for the LT1 - not sure if that's what you are looking at - but the "Air/Fuel Management" section is generically applicable many GM applications.

See if this helps:

http://members.aol.com/InjuneerZZ/ScanMast.htm

What motor? Lt1 or Ls1?

thank you very informative and did answer my question