Greetings all,Today I tried to fly from KRNO-KLAX on the -700. I programmed the FMC as I normally would, with a cruise altitude of FL370, and had approx 12000 lbs of fuel (a bit high, but it was a VATSIM event and I was prepared for possible enroute holds). I noticed during the climb the indicated airspeed was unusually low, perhaps 160kts or so, all the way up to the planned cruising altitude. I tried both Vnav and speed override on the MCP, but it didnt really change anything. I went with Vnav hoping the problem would clear up. Then, I went right thru the FL370 ceiling although the altitude indicator on the MCP was showing 370. At this point I was up and down, with the v/s indicator fluxuating wildly, never settling at the 370 altitude. I had to finally take it off auto-pilot and divert to KFAT. 2 questions. What might have caused this problem, and during a diversion how can I re-program the FMC to show the new destination airport?Many thanks,Ron

Not 100% sure Ron. What was your FMC showing for your OPT/MAX levels? What mode were you using to climb to your cruise altitude? In this climb I would have engaged ALT HOLD and set the speed manually. Checked OPT altitude and then engaged LVL CH or VNAV.I'm note sure why you would bust the MCP altitude other than the A/P not being engage and or you being in an active climb mode to capture the altitude. Best,Randy J. Smith

Ooooops,Now that I think back, I was given vectors to the first fix, and then told to procede as filed. I think I "might" have gone to VNAV/LNAV without engaging the autopilot. D'OH!!!! That would explain it all. Stupid, unfortunate error, kind of like taking off from the wrong runway, but in my case it was all a simulation. :-(I'd still like to know about re-programming the FMC for a diversion. Ron