I just though t this thread might help somebody who might have misfire issues with their TD5.

My Defender was misfiring. Not regularly, but coming and going. It was really annoying. The unregular nature of the misfire lead me to believe it was an electrical issue. The wiring loom under the rocker cover that feeds the injectors. So I cleaned the oil out of the ECU connector first (under the driver's seat) and then took the wiring loom out and took it apart. I couldn't see any problems with the loom so I replaced everything back together. The problem persisted. I then changed the injector seals and copper washers.

The problem persisted, again on and off for about a year. I was still convinced it was an electrical problem so I took the injector wiring harness out form under the rocker cover again and stripped it down. Easy to do. I started tugging at the wires at where they feed into the injector connectors. One of the wires to the first connector was not crimped in at all and lose. I had found the problem. I soldered the wire back in place and fitted everything back. Worked a dream. That was a year ago and truck running perfect.

So, before you go doing anything drastic with your injectors, if you have misfire issues, give that old harness a good tug. A visual inspection might not show up the problem. You don't need a new harness, unless you do mind oil leaking into the ECU connector under the seat. My truck is a 2000.

I hope this helps...