code P1400,knock sensor,and O2 sensor 1...

[Holvinator]

are the codes that are appearing when they hook an OBD2 onto my 95 240sx se. I already changed the O2 sensor so it doesnt show it anymore. But my car keep turning off on me.

Don't know if any of those sensor are the ones causing my car to turn off while driving. Anywaysss, which one of them should I change first? knock sensor its $130 easy to install. Solenoid valve sensor...(Im guessing is the cam sensor or timing sensor for some people) its for $40 and almost $400 to instal in the dealer. I was told that since my car (which I bought it used and they altered the speedometer)has over 110,000mil I also have to change the timing chain....

Any inputs will be appreciate it. Thanks alot... planing on getting it fix this weekend