diss

my m.reg fiesta 1.3., fuel gauge and speedometer suddenly drop to zero for short periods as i drive. this is a momentary fault - the engine seems to choke momentarily as the needles drop back and then flick up again!!! the local garage have been helpful suggesting an earth fault and cleaning terminals on an earth cable but the fault reappeared after this work seemed to solve the problem!!
the vehicle also knocks as i drive-particularly on a rough road surface. the sound seems to come from the boot area. nothing in the boot. spare wheel is tightly fixed. it seems like the suspension is coming through the bodywork. shock absorbers do not seem faulty. any suggestions would be gratefully received with thanks!!!!!!!!!!!!