i have a serious problem with my focus. yesterday i was driving along when the car started jerking violently. it would do it for a short while then stop. i also noticed the immobiliser light (the one beside the clock) staying solid red and sometimes blinking only when the car is jerking or starts to die. all the needles drop sometimes and when the headlights are on they will dim a little bit. the battery light also comes on followed by the oil light. the car will also cut out at low revs for example if im slowing down at a junction. the speedo needle has been going crazy recently. say im doing 40mph it will shoot up to 120mph and go all around the place. this morning the car cut out and i could not get it started again. if i turned the key there was only a click coming from the engine. i had to push start the car to get it going again. can anyone shed light on this problem. i was thinking speedo sensor.