04 ls not running right

I have a 04 ls that has been with a mechanic who gives up. The car idles fine but has no power or acceleration all COP's have been changed. Also the computer is not throwing any codes. Mechanic says that cylinder 3,2,1 have sever mis fire and are pretty much dead but dose not know why. PLEASE HELP

Is your LS a V6 or V8? Has he removed the upper intake to access the coils (assuming a V6) and carefully inspected the wiring for the coils?

-Rod

Sorry thought I put engine type down, it is the V6 model and yes my mechanic checked the wiring he finally gave up and told me I would have to take to the dealer. I thought I would see if any one could help out before I went that route. Thanks in advance for any info.

Those three cylinders on the V6 are all Bank 1. Were there any symptoms leading up to this such as a loud band, or rattling noises, etc.? It seems unlikely that a mechanical issue would take out only 1 cylinder bank.... You should have a compression test performed on that bank, check for power and trigger to the CoP connectors, and finally check for pulse to the fuel injectors on bank 1. That information would help identify the next path to go down.

-Rod