For the last 4 months we have experienced rough running at start up from cold.  It lasts around 60 seconds before settling down to something far more acceptable.  Miles : 79k.  Wet belts : done last year.  Fuel : does it with either E10 95 or E5 97 in tank.  Have already run several bottles of 'redex petrol treatment' through system ... no change.  It is getting worse ... slowly ... and I have been waiting for DTC to appear ... but it hasn't ... yet.  Have plugged in FORScan ... and analysed DTCs ... nothing in the PCM module.  And setup a dashboard and run several log files.  I am NO expert on fuel injection systems ... so I have simply only been able to look at the log data and see if I can figure 'what's changing' at the point of improvement.  What I have noticed is ...

1. The Desired RPM (DRPMIS) up until 'smooth' is 1200; it then reduces to around 1000 and then 900 in increments of 10
2. The fuel pump (FP) is always 100%
3. The fuel rail pressure - low range - sensor (FRP_LRS(V)) is always 5 ... always
4. The fuel rail pressure (FRP(kPa)) - bounces around 7000 - 9000 during 'rough running' period ... with the FRPS(V) at around 2.1V ... reducing to around 1.1V when smooth
5. MAF (g/s) ... is ~ 4.5 when 'rough' ... and ~2.2 when 'smooth'
6. MAFHZ ... is ~ 2900 when rough ... and ~2100 when smooth
7. SPARKADV (degrees) ... is .. very interesting ... 
   1. 0 to 5.5 to 0 at initial startup (0 - 0.6 secs)
   2. 0 to -11 to 0 thereafter ( another 1 sec)
   3. 0 to 16 to 0 wildly ( another 5 secs)
   4. 0 to between -5 and -7 to 0 (another 60 secs)
   5. 0 to between 10 and 14 ( thereafter as it smooths out)

I'd appreciate some help in knowing whether these values are 'expected' ... whether any are indicative of the source of the problem ... or whether I'm looking in the wrong direction / barking up the wrong tree.  To me .. the one that sticks out like the proverbial sore thumb is SPARKADV. 

Thoughts / ideas welcome.

Thanks everyone in advance.

When were the spark plugs last changed?

Good point.  Just checked.  It was serviced on 8th January including replacement of the 3 plugs.  Be worth changing them again to cross them off the list of possible causes.  Could easily be a dodgy one or fitment of low quality items.  Will report back when done.

Yes, check they were actually changed too. Some garages shy away from them as they're worried about them being seized in.

Update: Changed plugs and one of the coil packs.

Summary: Problem gone ... for now at least.

What I did ...

1. Plugs.  These were supposedly 'new at service' in January ... 5 months ago ... and 2000 miles since).  One of the plugs was a nightmare to remove.  Although it initially loosened it was VERY tight as it unscrewed ... despite working slowly, using WD40 (other brands available), and going back / forth every 1/4 turn.  This plug came out with 'black' end ... suggesting that it has been running rich.  There was lots of detritus around the plug hole and in the thread ... which I vacuumed out using a self designed / 3D printed vacuum nozzle extension.  I then used mulitple oil soaked fibre-free rags to carefully and progressively wind in/out of thread in combination with vacuuming. The other 2 plugs ... just came out nice and easy ... and were white ... as one would expect.  2 white plugs and one black suggests that problem is not related to any of the common/shared components ... and specific to that one cylinder.

2. Coil pack.  The troublesome plug also had a coil pack with a damaged end .. the rubber had been forced / cut / bent to make it fit / go down the hole to the plug.  So changed it as a matter of course.

Comment: The new plugs went in a treat and coil packs refitted.  And what do you know ... so far ... the rough running has gone.  So ... my initial thoughts are ... and of course this may change as more testing / use continues ... whoever changed the plugs confused the tight thread as being a seated plug ... in other words the thread was so tight that the specified torque was achieved prior to seating the plug.  And ... if the plug was not seated ... then some of the thread detritus was probably the result of gases escaping through the hole rather than through the exhaust.  And may also explain (to some degree) the 'damage' to the coil pack rubber. 

Anyway ... I'll continue to monitor and report back if things go bad again.  But so far ... so good.

They probably just hadn't bothered changing them.

Glad you're sorted👍