TD5 15p misfire?

Hi All
My Defender 2005 started misfiring Today,Im thinking it the harness?
or maybe something else? never done one before so any ideas please, and a brief description
of what the job entails and the best harness to fit might help.

Is there any oil at the connectors to the ECU under the seat?

As well as the above excellent tutorial there are several very good youtube videos on this subject.
(The disco TD5 is the same procedure other than the ECU being under the drivers seat in a defender)

If not the harness, check your air intake system for water. There should be 2 valves in the system (one between the wing vent and the air filter, the other in the airbox itself) to allow water out, if these block spray/rain will get as far as the filter. I had a misfire in heavy rain a few years ago, turned out that both of my valve were stuck shut and there was water in the airbox, not a great deal but enough to soak a few sheets of kitchen roll. Dried out the box, flexed the valve so they operated correctly - no more misfire.

Thanks...Ok I was going up the motorway in torrential rain, following a truck for 40 miles yesterday
just 20mins before the misfire,I will check that in the morning
I have unplugged the Red socket and yes there are small traces of oil in the socket
then I took off the rocker cover and the socket there is soaked in oil, not sure if that's meant to be there or not?

I had oil in my loom 3 years ago, as a temporary measure, I was told to clean the oil soaked socket in the rocker cover and fill it with Vaseline, then reconnect. My loom is still oil free.

The socket under the rocker cover will be covered in oil which is normal. Oil getting down the harness wires is not, it is not unusual to have a very small smear of oil at the ecu end but wet oil is not good.
Look for other causes before changing the harness.

just the slightest glimmer of oil at the red plug, just making the bottom outside red casing shiny
nothing inside really, anyway, update, I have cleared the terminals with brake cleaner and dried them out, smeared a little vaseline
on and pushed them up, on restart I'm only missing on one cylinder now not 2/3
So should I just order up the injector harness? can this miss fire come from the top end connections only? not involving the ECU

It may be a fuel related problem, I had an intermittent problem that felt like it was only firing on 3 cylinders, I changed the injector harness and the fault was still there, it was a faulty fuel pump.

I had this fault after driving in torrential rain. I took out the air filter and it had practically come apart due to water ingress.
Check the air intake valves as described above.

Given the airbox a good check and clean, but it was bone dry, after cleaning up the terminals on the injection harness I got it to run much better, but after a 10-mile trip she was back to big misfire, so I'm holding out my hopes for a quick change of injector harness Tomorrow and hope to be back with some good news, but many thanks for the help so far...I do miss my truck

I had this a couple of years ago. After throwing a heap of time and money at it it turned out to be the ecu. If you can borrow one to swap out you'll know straight away if thats your problem..

Yeh, your right, I have spent a fortune on it today, fitted new maf unit and the top injection harness
won't even start now, Just got indoors frozen and had an awful day, I don't know anyone with a td5
and think that may involve some coding work that I don't have a clue about.
The biggest problem here is finding a decent mechanic,I'm happy to pay but there all clueless.

Feel for you buddy. My local specialist lent me a Td5 discovery ECU. It’s plug and play. No coding needed. But Fuel and temp gauges read backwards.

Thanks, mate, you know the score been out working all day in the wet and cold, go to the buy these parts
then do the fingers crossed when starting, and nothing
I might get my son on the case and see if there is someone around with a 15p ecu.
Thanks again much appreciated.

Check you are getting fuel pressure at the fuel pressure regulator (FPR) your fuel pump may be faulty.

Yes, you are right...I think, switched the ignition on today went around the back and no noise
coming from the pump, then I tried the purge trick with the throttle pedal and still no action from the pump
I have ordered one up (genuine ) and should get time tomoz to get it on, thanks for all the excellent comments thus far, a real help chaps
will be back soon with a positive, I reckon

Latest ...turns out the plug on the pump was loose, I have owned the truck for 5 yrs and in that time the plug has never been pushed home and clicked in, so I'm thinking that was the reason for the misfire and finally blow the fuse,
I can take the new pump back for a refund, however, after fitting the new injection harness and a new MAF sensor I'm back to full power and shes running and pulling like a train. Thanks again to all that participated with my problem.

gary brion said:

Latest ...turns out the plug on the pump was loose, I have owned the truck for 5 yrs and in that time the plug has never been pushed home and clicked in, so I'm thinking that was the reason for the misfire and finally blow the fuse,
I can take the new pump back for a refund, however, after fitting the new injection harness and a new MAF sensor I'm back to full power and shes running and pulling like a train. Thanks again to all that participated with my problem.

Click to expand...

Great news, thanks for the update.