Hi again, I'm in the UK, the car was buillt at the Honda plant at Swindon.
It is a Honda Civic manual transmission ,diesel, 1.7 CTDi. (I'm struggling
to find a workshop manual for it on the internet or anywhere else)  It was
registered on the road 2003 and has done just under 71000 miles. Three weeks
ago it fully passed it's MOT (roadworthy checks + emission checks). Fuel
filter was changed at the last but one service so one is due at the next.

Looks like it was in limp home mode. It's changed now though - after leaving
it overnight the engine warning lamp is still on when the car is running but
the car will now happily rev as normal. Presumably there is still something
wrong.

With little other info I'm assuming it's an exhaust detector fault of some
sort. Getting free fault codes read is a bit tricky over here - presumably
manufactureres have their own interface and comms codes or is there an
industry standard (eg connector pinouts and codes etc ?) Might it be
possible to get software and a laptop interface lead to connect to it ?

There is a section of the exhaust pipe that looks like it might be a CAT
converter (it's about 8 inches long with metal thin strips, cross platted
around the outside.)  When tapped it has a slight rattling sound from
inside. (Hmmm  $$$ £££ ?).  Is there an emission detector after the CAT
(assuming it is one ???) I have had a good look underneath and can find
nothing so assuming there is some form of emission sensor it must be close
to the exhaust manifold (???)

My next step is to look for any detector and test it and try and get any
fault codes read (without spending a fortune on labour charges). I read
somewhere on the newsgroup about the car's computer forgetting any fault
code conditions after the car has been started three times - sound like a
myth or crap design ? I wondered, if it is true, if that is why the revs are
now ok.

Thanks for the advice/suggestions - any further to be offered would be most
gratefully received.

Regards,

Bob