Help! - Strange tickover problem ...

[WilliamsII]

Help! I've got a WilliamsII that's developed a strange tickover problem. If I drive up to 4000ish rpm the tickover is fine at 1000ish rpm. If I drive over 4000 the tickover goes up to 2500ish rpm and won't settle back down unless I flick the ignition on and off (eg shutting the sensors down). It doesn't seem to happen if I rev the engine when stationary so I think it's something to do with road speed. Does anyone know if there's a sensor that picks up on this - something to do with the speedo? I've changed the CTS and Idle Valve and it made no difference but I didn't really think it would anyway. I think something is telling the ECU that I'm still driving when in fact I've come to a standstill. Any help greatly appreciated as it's driving me mad!!!

[MatBrown]

Yeah, there is a road speed sensor on the speedo cable behind the dials.
These can sometimes be re-earthed to cure the problem or you might need a new one.


Mat.

[WilliamsII]

Thanks Mat. Will have a look as soon as we get a decent day. Is it actually part of the Speedo cable or separate? The reason I ask is that I'll make sure I've got it before I take it apart so I'm not waiting around. I guess I can get the cable all over the place but if the sensor is separate what's the best place to get that - I usually come over all feint if I have to go anywhere near a main dealer!

[MatBrown]

It's part of the cable.
Main dealer only i think.


Mat.

[Chadwick]

I had the same problemo.

Dash off, splice the black cable that pluggs into the back of the speedo/rev dial box, and earth back to a peice of metalwork.

Worked a treat. Better than a £110 cable from renny.

[WilliamsII]

OK thanks. Still waiting for a decent day (eg dry!) but will update when I've done it. How can they charge £110 for a bl__dy speedo cable. I don't suppose anyone knows where else to get one, none of my local motorfactors list one for the 2.0?

[WilliamsII]

Result!!! Worked a treat and only one 'spare' screw! - thanks. For anyone else who has this problem this is what you do ...
1. Remove dash top
2. Remove steering column cowl
3. Undo speedo binacle screws (2 at top, 2 at bottom which you'll need a torch to see). The bottom two you access by going up by the steering column where you've removed the cowl.
4. Pull speedo binacle forward so as you can see the speedo sensor at the top of the cable.
5. Snip the black wire where it comes out of the sensor, extend it and earth it somewhere with a self taper.
6. Put back together, bandage fingers/hands where necessary, have a cup of tea and congratulate self on job well done.
7. Nearly forgot, go for a drive and hope all's well. If not a new cable/sensor might be your only option ...