Volkswagen: hunting, volkswagen jetta gl, volkswagen jetta

Question
my 1998 volkswagen jetta GL is hunting when idle.  it cycles
between 600-750 rpm.  Then it drops lower and
overcompensates, etc...  When i press the gas I can also feel it
cycling, it looks as if it maybe cycles 50 rpm up and down when
the gas is held constant.

Answer
it sounds like a possible throttle body fault (the part which regulates air flow into engine). it is quite common for the bore to become clogged with carbon and sludge. you would need to remove the throttle body ( usually held on by 4 5mm allen key studs, a few pipes including water pipes and accelerator cable or multi plug). then open the butterfly valve by hand and use thinners or similar to rem ove the build up from around valve. once it is cleaned, refit it. turn the ignition on and leave it for about 30 seconds before starting as this may allow it to reset itself. on occasions the revs have been known to stay at about 1200 rpm on tickover until the throttle body settles in again.