flying atr flight1 on fsx it is impossible navigate with autopilot in lnav mode because the aircraft proceeds left and right at zig zag and it is not able to folow the route, very strange mode, someone could help me please?

How high the route? Winds aloft? Which ATR?

The last time I flew the Flight1 ATR was many years ago in my FS9 era, but when I read this post I decided to try it again in FSX. So today I carried out a complete flight after programming it into the FMC and I have to say the autopilot followed the planned route perfectly with no deviation or zigzagging. I am not sure therefore why your ATR will not follow your programmed route. Have you previously been able to fly the F1 ATR without these problems or have you only just started using this aircraft?

Despite its age and the fact that it is basically a port over from FS9, I had forgotten how enjoyable the Flight1 ATR is to fly and this remains so in FSX. Although, in terms of eye candy, the VC visually is nothing like as good as the Carenado ATR-72, it is still quite acceptable, and the level and accuracy of systems replication in the F1 version seems better. The Flight1 ATR also has a very low VAS footprint which is a great advantage in FSX, with its 4GB VAS limit. This allows flights to be made into resource heavy addon airports such as Aerosoft Frankfurt without the risk of the OOM errors which can plague the Carenado ATR when used with addon airports such as these. 
Bill