Spark plug lead confusion - please help

[ryan72]

Servicing the engine today, changed the plugs then came to changing the leads.

I changed the whole rail over, plugged in the leads into the correct plugs.

This is the bit im confused with..


why is there abit attached to the old lead?? I cant remove it from the old lead and it runs right across to the airbox area?

On the new lead rail there is 7 leads to plug into the 7 bits on the distribution cap.

So what do I do with this 1 random part??

[Brianmoooore]

If your new leads are genuine, they will have this part on them. If they are aftermarket, send them back where they came from, as being 'unfit for purpose'.
I have never yet found a BMW spark plug lead that has deteriorated. The only ones I have ever changed have been because of physical damage, usually caused by someone removing leads from the plugs by pulling the wire rather than the cap.
The 'bit' in question is a sensor that detects when #6 spark plug is fired. This is the equivalent of the cam position sensor on later engines, and enables the ECU to fire the injectors semi sequentially, under certain conditions, instead of all at the same time.
Your engine will run fine without this sensor in place, but will run that little bit better, and use a little less fuel to do so.

[ryan72]

I have opened the lead packet now, and it says on it - once open, no return available

So I could just use these new leads, and not run the sensor, and everything will be fine? Just not run 100% correctly, and use a little more fuel?
If not im thinking of maybe using that #6 lead with the sensor along with the new leads possibly.

Reason why Im changing everything is because it has't run since 2004 and was mis-firing so thought I would start by changing all the sparking components to see if that helped

Thanks for your reply

[Brianmoooore]

I have opened the lead packet now, and it says on it - once open, no return available

They can write whatever they like on the packet. If they were advertised as being suitable for your car, they are unfit for purpose, and are returnable!