Rough idle/running mystery

[caercamper]

Hi all

Really scratching my head at this now. In the autumn I had a leak in the high pressure line from the pump to injector no 3, with accompanying misfire and rough idle. Fuel line was cracked at the union with the injector which was replaced at the time but the rough idle and misfire has never gone away.

So far garage has:
- Replaced injector no 3, and swapped a few around to try different ones
- Checked valve timings and adjusted
- Replaced cylinder head gasket (which had leak between coolant and no 3 cylinder)
- Checked cylinder leakage past pistons - 3 is no worse than others
- Checked valves - all sealing properly and clean from coolant leak above

Compression is slightly down on 3 but again not massively.

They're now a bit stumped although still looking. I'm told by my local injection specialist that the Bosch pump can't be to blame as its centrifugal (?) so any issues would affect all cylinders equally.

Any ideas or experiences from anyone that could shed light? It evens out with revs, although I think it still lacks a bit of power at speed, but the idle is pretty rough.

[Chug]

Whilst the pump is rotary and not linear(wouldn't really call it centrigugal) but it is possible for it to be causing a misfire, for instance if part of the plunger for that cylinder is damaged, so it might be worth getting the pump tested as it seems the only thing you haven't tried.