No video signal

[nino5]

the monitor shows "save energy mode"

1- i did replace the cable
2- i did check the monitor with other "cpu"
3- i did replace the vga card which is pci .... but still does not work

the computer turns on by it self when i plug the power cable....

 

[enzo matrix]

Hang on, let me use my psychic powers to find out all the other relevant information including your system specs, monitor and what cable you are using (VGA or DVI etc)

Things I don't understand from your post:
-replacing the CPU would not change the result. Did you perhaps mean other "computer"? I am going to interpret it as such and interpret that through the test you found out the monitor is fine.

In the meantime, try and see if anything here works:
-try the integrated graphics if present
-are there any beep codes on boot?
-pci eh? sounds like an older computer. How old is it?
-try the video card in another PCI slot
-double check that the PCI card is working by trying it in another computer.

 

[shortstuff_mt]

Enzo matrix is right, we need to know your complete system specs in order to be of much help. Here's a checklist that was created to troubleshoot this exact type of problem:

http://www.tomshardware.com/forum/261145-31-read-posting-boot-video-problems#t2091479