Center image on left side and don't know why

Are both speakers exactly the same distance from you?

I had this issue recently, it turned out the midrange driver on one side was not working properly. It was a simple internal cable issue, but it made me nuts until I found it.

I agree with Twl, in first order I would look at electronic problems in one channel of your preamp or source output.
(Have you swapped cables all the way back to the source?

The most important thing is to narrow down where the problem is coming from (obviously). Try switching left and right speakers. Does the soundstage then move to the right? Then try swapping left and right connections on your preamp. Etc.

I have this problem too and concluded that in my case it is a room/speaker placement problem. My "center image" is usually 3-5 dB to the left of center (but it varies with music). I can center it by moving my listening position, but don't like this solution in my room, so I only use pre-amps with balance control.

Some good pre-amps with balance control are Sonic Frontiers Line series, ARC LS-25, and Levinson SS pre-amps. I use the SF Line 2SE, and there are several good but inexpensive pre-amps with balance control, ie Adcom. Cheers. Craig