Nissan Repair: 2001 Nissan Altima GXE, mass airflow sensor, air control valves

Question
I have a 2001 Nissan Altima GXE.It has 94k miles on it.There is a pending code of P0325 Knock sensor circuit malfunction. The ses light is not on(I read somewhere that the knock sensor will not cause light to come on)The car will idle erractly from about 750 rpm to almost stalling out. There is no problem  with engine performance otherwise.It has great take off  with no other problems. So it seems to me that the problem is related to idle and other circuts that may cause the idling problem. I have read other forums and there seems to be problem with a bad run on knock sensors, intake gaskets,sticking idle air control valves etc.This is a head scrather.Any help? Thanks!

Answer
Glenn,

It seems that you have a couple of problems coming up.  The first is the knock sensor.  Yes, Nissan had a bad run of knock sensors and I would just replace it and reset the computer.  True, the SES is not on but you have an intermittent knock problem that the computer is sensing.  Two things can happen.  The car will go into limp mode where it retards the timing to keep the engine from beating the rod bearings out of the engine.  Second, it will not retard timing and the engine will eventually suffer rod bearing damage and even more depending on how bad the engine knocks.  The second problem you have is probably the mass airflow sensor that is causing the erratic idle.  Yes, this is expensive and no codes are set so you should verify before you plunk down the cash for a new mass airflow sensor.  Just did an Infiniti I30 and it was the mass airflow sensor that corrected the idle problem.  I hate to say it but you should go to the dealership and get violated for a computer reading.  They have a Consult II Scantool that will verify what needs replacing.  Now, you are out the $100 for the computer diagnosis and you can purchase the part yourself and replace it.  Then, reset the computer and you are done.