2012 TDCi Engine RPM varying ("Heartbeat")

[AlCan]

I hope Just Bill isn't lurking here - after his nightmare, I bet he's had enough of Mondeo's to last a lifetime - and he probably won't want to see this.

Anyway, in one of his earliest posts, he described this. I have the same / similar thing on a different car.

Not the same extent of power loss, but I'm sure, it's a progressive thing. I suspect there will be a lot of agreement on the cause and the solution, but how about the explanation? I have a theory...

https://photos.google.com/share/AF1Q...NqbUVpdVZ0TWdR

Tried to keep the throttle as constant as possible, but still got an acceleration from about 48km/h to about 67, stable in the last half of the video.

Tried it with Cruise Control but found manual control showed it better. It's very hard to distinguish any change in power level, but sometimes you can feel it, especially during decel, surprisingly. As you can see, this was in 3rd gear, but happens in all (higher gears anyway).