Toyota Repair: 94 Camry 4cyl codes 12, 13, pcv valve, engine knock

Question
Hi Ted,
I just purchased a used 94 Camry 4cyl 75k auto, and did the timing belt (idlers, seals, belt), tune-up(plugs, cap, rotor, v/c gskt, pcv valve, thermostat, 2 spark plug tubes #1 and #3) after purchase.  About a month later the check engine light came on and I pulled codes 12 and 13. (Engine Knock control cpu and rpm signal).  I am contemplating changing the distributor(looks fairly new), though after reading all your answers to previous posts, I am wondering if you think the IAC valve may be the problem.  Should I clean it first?  Most of the time, it runs fine, though once in a while, the car starts jumping/ missing (rpm gauge will jump around to 2.5k+ without motor surging) and the car would eventually die.  It will have a hard time starting after this, though, if I do short cranks on the motor, it will start again and run very rough while putting load on the motor.  While idling, it usually runs fine (though slightly low idle).  I called a couple of my mechanic friends, and they suggested replacing the distributor (though the one in the car looks relatively new).  One of my other friends told me that the 92-95 Camry's have a chronic computer problem and this may be the cause.  What do you think?

Answer
The DTcs 12+13 are both directly related to the rpm signals to the computer, I know of no chronic problems with the ECMs on this model but I do know that there are a lot of distributors that have caused problems in the past so I recommend that you replace it.