Engine bucking when its hot outside

I'm at my whit's end with the junkyard motor (EJ22 from a '95 legacy wagon). It runs perfect, unless of course its hotter than hell outside. Engine temp makes no difference, it is outside air temperature.

 

Every morning, it drives great (60 mile commute btw). If its 100 degrees or more on the way home, it will throw the CEL and buck (violently at times). The CEL is P0341 or Cam Position Sensor. I can clear the code, and this process will repeat any given day. One day when the high was only 95 it didn't happen, and it had never happened before this long extremely hot spell.

 

The symptom mostly occurs in higher load at lower RPM like going up a mild hill at 70MPH. High RPM driving seems OK - above 3500 seems just fine.

 

This weekend I'll take the timing cover off and make sure its aligned properly. Any ideas what else to consider?

I'm posting my results in case it may help some one some day. I tore into the timing belt today and found that the crankshaft timing sprocket was one tooth off.

 

Also the timing cover was broken and the tensioner pulley was installed only finger tight. This leads me to beleive that it was just installed poorly, and it took the excessive heat to make it run badly enough for me to notice.

 

Its not hot enough for me to say for certain that it won't buck when its hot weather, but I suspect it won't. Already improved are idle while in gear and part throttle torque.

Glad you found it before it could do any damage. Thanks for the heads up.