Accelerator Loss 99 VW JETTA TDI loses accelerator, goes into high idle. Sometimes restarting will correct, but getting worse. Cruise control will hold speed position even when accelerator is not functioning. Manual transmission will allow starting the car while in motion, and the accelerator will return to functional use as long as the gas pedal has pressure on it.

Go back to that VW dealer and complain. I'm sure you payed plenty, and I know in my shop, if a customer's car is not repaired to their satisfaction, I want to know, and make it right. Sometimes parts can be bad right out of the box, and sometimes problems are misdiagnosed. Go back, but don't agree to pay for anything untill you get a satisfactory explanation. Good luck.

Sound like you could have a defective ISC (idle speed control) sensor.

this may not be the answer you want but as all vw product are computer controlled you are best to get a diagnostic done at a dealer that has the machine(a proper vw one)you dont have to get them to do the work but its so simple once diagnosed correctly.....and a small price to get the correct info first time.
you can buy the all in one type,but they are not available here in the U.K.so i dont know if they are any good...
i am a fully qualified technition but still go to my local dealer for it to be done(cheaper than buying a diagnostic )

CODE PO301 - CYLINDER NUMBER 1 MISFIRE DETECTED. POSSIBLE CAUSE- BAD COIL - SPARK PLUG - INTAKE MANIFOLD VACUUM LEAK - DIRTY OR FAULTY FUEL INJECTOR. CODE P1142 - DID NOT SEE. CODE P1545 - THROTTLE VALVE ACTUATOR MALFUNCTION.POSSIBLE CAUSE THROTTLE VALVE CONTROL MODULE FAULTY - THROTTLE VALVE IS DAMAGE OR DIRTY - THROTTLE VALVE MUST BE IN THE CLOSE POSITION - ACCELERATOR PEDAL OUT OF ADJUSTMENT. THROTTLE POSITION ACTUATOR IS SHORTING TO GROUND OR POWER.

I pulled my switch out of the dash and sprayed it with contact cleaner. Air dry and put back in. 2 years without a problem. If you're not electrical savy, I'm pretty sure there was a recall on that, and it should be replaced for free.

check /replace the fuel filter and check the fuel pump pressure before and after the bleed valve to the throttle injectors

check catalytic convertor

In the VW world it's called "Limp Mode" and unfortunately it's relatively common. Here's a link to some useful info on limp mode

http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm

Also check out www.tdiclub.com - these guys know their TDI"s...

Check for intake blockage (coking). May also be a bad turbo-charger actuator pod or something as easy as a Mass Airflow Meter.

these cars are fitted with a fly by wire accelerator pedal that is controlled electronically by the cars computer it is possible that there is a computer problem or the throttle body ( air intake system )or accelerator pedal is playing up.
it is highly possible that the car is doing exactly what you say it is i recommend you take it back to VW and demand that they take a proper look at it you might have to leve it with them for a couple of days and get a service advisor to drive it home so as they can see the problem ocure.
regardles the cars computer should of thrown a code declaring a fault in the system witch should give the tecs some were to start looking.

good luck with this problem if you have any outher questions let me no