I've an intermittent issue with my 2004 1.9 TdI - on occasion it will start but only tick over and not respond to the throttle pedal, over a number of minutes at tick over the engine starts to show reluctant signs of picking up revs when the pedal is depressed, and will eventually begin to rev and respond normally to the accelerator pedal. It then drives with no further issues - sometimes on restart all is well, and other times the problem re-emerges. At no time do any engine management lights come on. Any insights would be most welcome.