does the 25mfd capacitor on the coil feed do anything other than suppression? I dont have one fitted, but the idle is dog rough, so wondered if it was due to not having the cap...

nope and shouldnt affect idle.

things to check include..to start with are

Earth strap on engine.
the earth shiels on VR sensor and megajolt are only earthed at one end.
VR sensor correctly mounted and close to trigger wheel


Paul

Good spot Paul, earth strap is fine, sensor and wheel are standard zetec, but, I have the EDIS - MJLJ pip/saw shield earthed at both ends.

Any idea why this is bad? not doubting it just like to understand.....

As the ends will not be at exactly the same values at all times it creates small currents and can confuse the edis unit.

or something to that effect.

You can end up with an inductive loop - imagine the endless loop formed with the screening and the chassis. This can act like one side of a transformer, and interference will be 'received' by the loop and will in turn be passed on to the wires inside.

If the screening is only connected to chassis at one end, there's no loop to pick up unwanted signals.

Thanks guys, just reading a thread on autosport labs, which says VR screen PIP saw screens connected together and to pin 7 of EDIS only not to pin 9 as the diagram shows.

Thread

thanks again guys I might get a smooth idle this weekend.

[Edited on 16/12/08 by r1_pete]