when its misfiring the engine will exhibit a shake which you can see with the hood open. there will be a lack of power when driving.

misfire monitors run continuously and will set the SES light on immediatly. clear the code. start it up cold and drive it unitil the misfire occurs and note the conditions.

engine hot or cold
at idle or under load
intermitantly or all the time

 

This is the picture of the coil pack, I am not sure if I can try the screw driver test, I am afraid can blow the module. I will do what Tech2 is recommending, will clear the DTC and drive it to find out when is on again, will report back after the tryout. I know that this kind of vehicles clears the code after 3 cycles of code not being present so I am sure what I have done has'nt worked.

I did clean the injectors with an AC Delco additive.

I am reluctant to change the coil, I am not sure it will fix the issue.

 

the coils or module are the most likely cause.
the injectors are pretty reliable on these cars.
how are you clearing the code?

 

I will go to one of these part shops, I believe they can help me to clean the codes

 

I finally was able to do the tryout, the misfire occured on cold start. I cleared the code when vehicle was hot and did not came up until the early start up @ idle

 

I changed the coil and module, the SES light still on, but not sure if is a different code, the car feels with more power, so I guess there was a wrong coil. I will scan the vehicle again.

 

The coil fixed the issue, but now I have a new DTC P0171, will check for vacum leaks.