Speedo not working until 40 mph
Discussion
Could be knackered speedo sensor or the speedo itself. Worth cleaning the sensor and checking for funny wires. Beyond that you need a scope to check the pulse train coming from the sensor. Details in the Bilbe 2.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
Thanks Steve I'll have to get the new bible anyway so I'll check that out. It was working fine until the car went in to the dealer for a check on a slight misfire, after about 5 miles on the homeward journey the speedo started playing up. Is it possible for it to be caused by a loose connection in the loom somewhere? The car has to go back on Saturday for a new fan belt, I'll get them to check it while there I think.
apache said:
Steve, would this not affect the idle? mine has become a bit erratic by staying high sometimes, if I drag the revs down using roadspeed it does what it should, it also hunts
It all depends. If the sensor is going a bit intermittent it can be enough to satsify the ECU but not for the speedo. What you describe sounds like a stepper motor problem but it could be made worse by a duff speedo input. The only real way of testing that sensor is with a scope. It also means that you can see what signal is appearing at the ECU as well.
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