Speedo And Engine Spluttering And Backfiring!?!?

[Ali-jo]

I was hoping that someone out there might b able to answer a couple of questions? Occasionally my speedo drops to zero and this makes the radio quieten and the engine performance change. Also the engine coughs and splutters sometimes likes its in the wrong gear, but its not. And sometimes it sounds like its backfiring??. The fuel filter was changed and things seemed ok 4 a week and then it coughed and spluttered again. The car starts first time every time and runs ok apart from that. Any ideas?

[MrRedman]

its the vehicle speed sensor on the gearbox had exactly the same problem let the garage do it tho in case it snaps on removal