Once again, the speed hold on my CS 757-200 doesnt work! Im at Fl380, I want mach .84 and it wont go past 77.5% N1, and I keep slowing down, it wont hold .84, I even tried setting mach .99 and it still stayed at 77.5% N1, and im sick of the A/T not working, this is the second time for me, and I've seen 3 other posts on the A/T not working.

I don't think it is supposed to cruise at M0.84. I've never tried it myself though, because the cruise speed is supposed to be M0.80. I usually cruise at between M0.78 and M0.80 (depending on the Cost Index).

Friends, I personally use a CI of 71 and cruise at M0.800 at any altitude.

However, the 757 max speed is M0.86 above B767's M0.84, and I've put .84 or even .85 in the 757 FMC in the last leg of flights if I have enough fuel and it always keep that speed. I think if chose to set the speed hold at M0.90 I would overspeed without a doubt. So I don't really have a problem when selecting high speeds at cruise altitudes.

What is the Cost Index you've been using fsxking08?

Can you post a screenshot of the panel? This helps spotting possible problems.

There should be at least two methods for achieving the speed. When VNAV is off, set the speed window to 0.84 or when VNAV is on, set the desired cruise value in the FMC which should trigger the AT aiming for it.

Can you get to the desired speed with the autothrottle off?

I never use VNAV because it never works for me, and I cruise at Mach .84 because i hate flying slow, so I always add extra fuel and go .84, and the flight is done so i cant post a screenshot, and I barely use the 757 anymore because I've gotten a frame rate drop and 14 FPS is too bad for me, so I use it like once a month and I can get it with the A/T off, I had to manually set the throttle myself