300tdi throttle sensor gremlin

:doh: ok so kept getting engine managment light on my 300 tdi 97 disco auto but only when trying to keep at a constant speed, ie 30, 50, 70 whenever just trying to hold speed but if you take your foot off the throttle or accelerate it goes back to normal.... took it to local garage and plugged it in and throttle position sensor came up... **** they are expensive!!! So found a chap on here who had a used good one... swapped it over and same thing again... so down the local garage again and........... throttle position sensor???? now I am stuck and dont know what to do next! Anyone got any suggestions?

the chances of getting poor used pot is quite high so replacement hasnt ruled out throttle pot

surely not though.. anything else that can cause this?

turns out it was the battery all along

now fitted the 300 with a 100amp batt and its fine