Volkswagen Repair: 2001 Jetta TDI problem with check engine light, vw jetta, fuel injection pump

Question
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Followup To
Question -
I have a 2001 VW Jetta (1.9L turbodiesel engine) with about 80K miles on it and the check engine light has been coming on intermittently for about the past two weeks.  It seems like the light will come on in the mornings when I get up and drive it to work.  It will stay on when I drive to lunch but it will finally go off in the afternoon on my way home from work and be fine for the rest of the evening.  The car never idles badly, loses power, or puts out any smoke and it seems to be running perfectly normal when the light comes on.  I went by Autozone and they hooked up the handheld diagnostic tool which read "P1248 Manufacturer Control Fuel Air Metering."  When he looked up this same error message on the computer inside the store it read off the line "Turbo Boost Pressure not detected."  The VW repair book says that it is a "Injection Start Control Deviation."  I am at a complete loss as to what could be wrong with the car.  At about 45K miles the car started running terribly and the dealer replaced the fuel injection pump along with the control module (thank goodness the warranty covered it) - could this be something related to it?  I like the car quite a bit but am really wondering if I should get rid of it before I run into major problems.
Answer -
Nick,

Yes this could be related to your previous repair, but it may also be caused by carbon build up in the intake and intake manifold. The system seems to plug up and restrict the air flow and thus reduce the turbo chargers ability to increase horsepower.  This is caused by the constant use of synthetic oil.

Have it checked out and cleaned. Then try switching to regular oil (not synthetic) during moderate tempurature months (not too hot not too cold), I've found this works very well.

Also, check that your coolant level is completely full, this will send a fault when the engine is cold.

Good Luck,

Paul
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Paul,
I ended up taking the car to the dealership for them to look at because I couldn't clean the intake manifold and they said that they were getting two error messages - one for the glow plugs and one for the fuel injector pump.  The mechanic didn't tell me what the error numbers were but said that faulty glow plugs could cause the fuel injector pump error.  The dealer quoted me $530 to replace all four glow plugs which I promptly refused since the plugs are only about $30 each at NAPA and look pretty easy to change.  Could the glow plugs also be causing this problem?  The Bentley service manual shows how to check the to see if the glow plugs are faulty using a multimeter and I am borrowing one tomorrow to test the plugs.  If I find a bad glow plug do I need to change all of them or only the bad one (assuming I replace it with the same brand already installed)?  Also, is there anything else that I need to replace along with the glow plugs (i.e. some people replace the spark plug wires when they replace the plugs on gasoline engines)?
Thanks again,
Nick

Answer
Nick,

Glow plugs last about three or four years on average, grounding the threaded shaft and connecting a positive lead to the exposed end will allow you to test them without a multimeter. A spark indicates that it is good, and the tip will get hot and turn red. If nothing happens the glow plug is burntout. I would recommend changing the four in the head at one time, I never repace one at a time.  You might also want to change the black power bar that attaches to the glow plugs or check that each glow plug fits in tight. Also if you put antisieze on the threads, the job will be even easier the next time.

Good Luck,

Paul