My old ford escort turbo diesel engine gone poorly with a really bad struggling idle. Apart from this issue it ran fine. Plenty of power when driving it.
What caused this was trying to start it in winter with a frozen water pump. It didn't even turn 1 full revolution. It knocked out the timing, so i had to remove the head to check for bent valves of which there where 2 that i replaced and this is after the rebuild so something had happened to the fuel pump. I also stripped this down to inspect but didn't see anything wrong but after this start up test and subsequent replacement of the fuel pump it was obviously damaged somehow.