help,2000 frontier 4cyl the timing chain is not moving .

[gilltexas]

good evening,was driving home one day whan the truck turned off on me.started doing my investigations.took the head cover off,cranked it,chain is not moving and the twin cams are stopped too,chain is not broken it is in place.,so my suggestion is that a bottom sprocket broke or teeths are off.so i dont know if it is worth changing the sprocket because i think maybe piston did hit the valve,or should i just get a used engine.thank u for any answers

[574-240sx]

That doesn't sounds good. Can you get a socket on the crank pulley and will the engine rotate freely. If it won't turn and its siezed I guess the worst you can do it start taking it apart to see what happened.