Subaru Repair: Subaru Legacy GT check engine light, mass air flow sensor, air flow sensor

Question
Hi

I've got a 1997 Legacy GT with 131k miles on it.  Recently, the check engine
light came on and here are the symptoms: the engine is shuddering at idle, as
if misfiring, and the RPM fluctuates between 500 and 1500 or so.  There is a
loss of power on acceleration.  So, I replaced the following: spark plugs, spark
plug wires, camshaft position sensor, camshaft wheel, and fuel injectors.  The
code that came up when i plugged it in was camshaft position sensor, but
after all of that I still don't have the problem fixed.  It did get partially better
though after replacing the camshaft position sensor.  I don't really know what
to do at this point.   Please help!

Answer
If I understand right, you had a check engine light come on with a P0340(camshaft position sensor malfunction) code.  Or was it P0 341 (camshaft position sensor range problem)? Any ways Subaru has an updated cam and crank sensor update kit that I hope you used.  The only place you can buy it is the Dealer.  The cam sensor code can show up for a few different reasons. One being the timing belt has jumped and the cam sprocket is out of time with the crank sprocket.  Has this been checked? Also if the original problem was just a bad sensor but all of the other stuff was done maybe there is a problem with how it was repaired or the quality of the parts that were used.  Have you performed a cylinder leakage test to verify that the mechanicals of the motor are ok? Start with checking the basics.  Things that can cause your symptoms are faulty mass air flow sensor, faulty 02 sensor, sticky valves and more.  I am not suggesting that you throw any more parts at it but those are all things that should be checked/diagnosed and with out the proper tools and diagnostic equipment I am not sure how you will get it done.  The information provided by a generic code scanner is not very valuable. The code set may have nothing to do with the symptoms you have.  The best advice I can give you is to take the car to someone local that specializes in Subaru repair or at least Japanese imports and pay the money to have it diagnosed.  Computer diagnostics are not always a do it yourself venture.