C110 and Idle Smoothness values

[Redline]

Have cleaned the vanos solenoids and DISA valve which has had a tremendous impact on smoothness of power delivery as well more power and reduced throttle lag and better consumption. Having checked for codes thrown afterwards (none) I decided to have a scan through the Data Stream options on the C110 diagnostic tool.

The one thing that really stood out was the Idle Smoothness values on cylinder 5.
While the other cylinders were pretty much static, cylinder 5 was varying wildly from +2000+ to 1300.
The C110 has what it calls set point values of +200 to -200 which I take to mean acceptable values are within that range. All the other cylinders were within +/-10 and static.

So, I had some of the plugs and coils out today. Nothing seemingly amiss with the plug on 5. Nice brown deposits. No eroded core or ground conductor. So, I'm suspecting (hoping) it's the coil on that cylinder.
I realise now I should have done the obvious and put that coil on another cylinder to see of the problems followed it. Will do that but thought I'd ask for experience/knowledge/wisdom of others.

I can detect a little lumpiness at idle (it's varying either side of 700rpm but not by a lot). It doesn't seem to hurt performance, at least at the moment?

Coil or Injector?
Change or leave it?

 

[t-tony]

First option is, as you said , move the coil mate. Then try some injector cleaner though the fuel.

Tony.

 

[Redline]

First option is, as you said , move the coil mate. Then try some injector cleaner though the fuel.

Tony.

Annoyed that I didn't do that this morning. I show people how to fault find both systems and software by isolating the potential cause. Doh

 

[t-tony]

You can always do the same with the injector too, although not quite as simple to swap.

Tony.

 

[Redline]

You can always do the same with the injector too, although not quite as simple to swap.

Tony.

Don’t do plumbing any more after a bad experience changing a ball-cock