engine revving hard at start up

[rashmore]

When starting brothers 1.4 petrol zx, engine revs instantly to around 4k rpm. Tried to leave to see if clear but not. Apparently last time he started it, car would high rev, low rev and repeat on tickover.
Checked all hoses and appear fine but accelerator cable is pulled on slightly by mechanism controlling position, when engine is off. how do i test if solenoid/actuator working ? newbie to electronic ignition systems
Other components to check out ?
cheers

[phil02]

I might be talking complete nonsense here, I'm not a mechanic, but this sounds almost identical to the problems I had with my AX. When the engine has started, it would begin to rev itself as though I were prodding the accelerator every 2 seconds or so - very embarressing stopped at traffic lights as you get a lot of dirty looks!
This started to make the car undriveable after a while, eventually found it was the stepper motor (automatic choke) - this is attached to the throttle cable - which was old, worn and had let in gunge and muck - the sliding component would get stuck instead of moving smoothly, stay where it was for too long, then free itself abrubtly, go too far, drop back and start again, causing the revving at idle and also occasional juddering/kangarooing when driving.
New stepper motor was a 100% fix but not cheap at £135 from a Citroen dealer (a lot cheaper from GSF I expect - you live and learn!)
It can be dismantled and cleaned out, but if there's muck in it it means it's already knackered and will gunge up again pretty soon - mine lasted a whole morning before going wrong again, but can last a month or two if you're lucky.
Hope this helps
Phil

[rashmore]

Cheers
Yeah we've removed that box off and pulled it apart. Everything clean inside, gear mechanism moves ok, so wondering if is the motor itself or whatever sender issues the signal to control it.
Have got 309 so were wondering whether to swap box over to see if that - but then if that gets damaged....2 cars out of action
Have to try and circuit test and see if we can activate the motor in choke control box, or try and bypass to eliminate it - parts hunt here we come...

[Stuart McB]

Befor going to Citroen for any thing like a stepper motor try to get the part number off it. Bosch have the number stamped on the parts used [:D]. Then phone up your local Bosch agent and give the part number. You'll be surprised how cheap these parts are compared the Citroen. New Idel valve (stepper motor) form Xsara £138 +VAT Citroen [:(], £83 inc VAT and delivery (next day) from a Bosch ageant [:D].
Try www.autoteknik.co.uk

[LeFrog]

You mentioned that the accelerator cable is 'pulled on slighly by mechanism controlling position'. I intpret this too mean your throttle cable is too tight.
I wouldn't have thought that a dodgy stepper motor would let your car rev that high.

[Stuart McB]

The stepper motor will let the car rev as high as it wants. Belive me when mine first failed the engine would rev almost off the guage and then slowly come back to about 1200 revs befor settling down.