An update on the unusual engine problem I've been having with my 2.0
TDCi Focus (Pug engine). Someone might find it helpful in the future:-

About this time last year the car developed an intermittent problem when
the engine was started within 15-30 minutes of having been shut down.
The engine would start but idle roughly at about 600 rpm. It wouldn't
respond to throttle inputs and there were plumes of black smoke from the
exhaust. The dealer said there were no fault codes but changed the EGR
valve anyway.

The problem happened a couple of more times but throughout the summer it
was fine. Come winter, the problem re-occurred. I took it to the dealer
who did a PCM update on the ECU. This didn't make any difference.
Luckily the problem happened while at the dealer so the technician could
see the problem for himself.

They took the car in for a week and ran lots of tests under the
direction of Ford Tech services. They authorised a new set of modified
injectors (at £1000/set). When I got the car back it sounded like a
tractor. The dealer said that this was probably the result of the
modified injectors and was the price to pay for having the original
problem fixed. Unfortunately the original problem was not fixed and the
car went back in again.

Ford sent out a field engineer to look at the car. Apparently they can
switch off each injector in turn and calculate the performance of each
one. For reasons I'm not sure of, the performance is expressed as RPM.
All four injectors should be within a few RPM of each other. On mine,
injectors 1 & 3 were 300 RPM down on the other two. So two of the new
injectors (Siemens) were defective. That would account for the tractor
like clatter at low revs.

They also replaced the throttle body. The technician had wanted to
replace it on its first workshop visit but Ford wouldn't authorise it.
The technician showed me the problem with it. The butterfly is spring
loaded open but when pushing it fully closed, sometimes it would stick
in this position. The Ford field engineer authorised its replacement
second time round.

I now believe that the throttle body was the cause of the warm start
problems and that the original injectors were fine. Its now had six new
injectors. Thank God its under warranty.

Finally, when it was in for its first visit, the technician had said how
awkward the glow plugs were to get out. I asked if it was worth me
paying for a new set for him to fit, being as they were out already. He
said it wasn't worth it as they looked fine and they were there for
emissions reasons more than anything else. When it was in for its second
strip down, the technician felt that the 7mm flats of the glowplugs were
looking a bit chewed up by now so he fitted a new set FOC.

The car is sounding quiet again now and the next week or so will tell if
the warm start problem is finally fixed. Fingers crossed.