road speed box

[chris212]

After renewing the stepper the tick over is much improved but still occasionally rises to 1800-2000 rpm at stand still after a run. Speed sensor on rear crown wheel cleaned and correctly gapped also. I can only think its the road speed box behind the dash?
I have found previous posts in this where Blitz and s.heath where developing a fix but the trail has gone cold?
Anyone know how to test/repair, and find! The box?
Its a pre cat with a T5 box.
Thanks

[davep]

Chris pre-cats didn't have a 'box' fitted. Because yours has had a T5 slotted in I'd first establish how the road speed signal is fed to the ECU since the integral speed sensor on the LT77 did the job previously.

[chris212]

I'm pretty sure its had the box from the T5 doner car, as well as the road speed sensor fitted by the diff. This also supplies the signal to the speedo.

[blitzracing]

1800- 2000 is too high to be a speed signal- from memory its around 12- 1500 rpm. You could wait until the engine is warm and ticking over nicely, then unplug the stepper (engine still running). Then drive around like this for a while and see if you get a lifted idle. If you do its, not the stepper or ECU causing it. You can run without the stepper connected, but you will need to hold the throttle open a bit to start the car and keep it running for a short while on a cold engine. I do have a modified speedo box laying around- but TBH, I need a definitive example of a faulty to one start with before I try a swap - ie either RoverGauge shows a speed reading when the car is stationary, or ECU mate shows the car is not in idle mode when its stationary. Also check the throttle pot voltage.

Edited by blitzracing on Saturday 10th October 19:49