TD5 problems in the wet

Hi All,

I have an issue with my Defender TD5 which only seems to occur in very wet and raining conditions. The car splutters at first and then I lose all acceleration, leaving me having to pull into the side of the road. It happened about a year ago and was completely fine the following day when it was dry and has been fine since, until 2 nights ago. Driving home in heavy rain and the car started to splutter, the engine management light came on and I again lost all response from the accelerator pedal. The engine was ticking over sweetly but the accelerator pedal produced no response at all - it was like it wasn't even connected. Turn the engine off, turn it on again, try again and the same thing happened within a few seconds. Turn off and on again and I could rev it fine, but try to pull away and out it went again with the accelerator being unresponsive.

I can handle most repairs on the landy, but this seems electrical and there my knowledge ends and my journey ended on the back of a recovery truck. The roadside mechanic was also completely baffled (but I'm not sure that he had ever seen any engine before) - he did at least plug his diagnostic tool into it and it came back with a range of faults including on the air conditioning and tachograph which is odd as neither have ever been fitted to this car.

Can anyone help with any ideas of the fault? The car is running fine again now, but it will rain again and this makes me nervous.

Thank you

There's a couple of issues poor earthing and harness for the injection is oil soaked. Worth checking the red ECU plug for oil contamination. Earth wire can fray over time, so try adding an extra heavy wire to see if that eliminated the issue. Another is water ingress into exposed electrical points.

Thanks Saxavordian. Would a good spray of WD40 over any electrical components do any harm?

The tachometer fault is usual on these things, because it's not fitted on the Defender. It probably originates from the fact that the software and ECU are very similar to what was used on the Discovery, which does have one. Although the ECU part numbers and fuelling maps are different, they still have enough in common to do this.

If the MAF/airflow meter fails while you're driving around you'll get a momentary hesitation but the engine revs will generally pick up again. It also puts the yellow light on and leaves an aircon fault for your fault code reader to find, although it is nothing to do with the aircon. You can check what the MAF is reading with the engine running via a Nanocom or similar device and if it's zero it's not working.

The TD5 is also prone to wiring loom failures between the accelerator pedal (or 'driver demand') and the ECU. These manifest as a failure to respond to the accelerator and a yellow engine warning light. If it's worse in the wet this might be part of the problem as the water gets in those corrugated plastic tubes Land Rover used to cover the wiring loom, and with salt on the roads at this time of year it might be shorting. The wiring on TD5s is comprised of conductors that become hard and brittle combined with insulation that gets hard too, and flakes off. Land Rover must have had a weird batch of wires from their suppliers. I've ended up fitting a whole replacement red plug loom and deal with failures in the rest of the wiring on a piecemeal basis as they come up.

Yes, of course there's the usual problems like oil in the wiring loom under the rocker cover, verdigrised earth points , fuel feed problems and much more.

Wet weather could just be coincidence. When car will tick over but won’t accelerate when pedal pressed could be a faulty throttle position sensor

Brown said:

The tachometer fault is usual on these things, because it's not fitted on the Defender. It probably originates from the fact that the software and ECU are very similar to what was used on the Discovery, which does have one. Although the ECU part numbers and fuelling maps are different, they still have enough in common to do this.

If the MAF/airflow meter fails while you're driving around you'll get a momentary hesitation but the engine revs will generally pick up again. It also puts the yellow light on and leaves an aircon fault for your fault code reader to find, although it is nothing to do with the aircon. You can check what the MAF is reading with the engine running via a Nanocom or similar device and if it's zero it's not working.

The TD5 is also prone to wiring loom failures between the accelerator pedal (or 'driver demand') and the ECU. These manifest as a failure to respond to the accelerator and a yellow engine warning light. If it's worse in the wet this might be part of the problem as the water gets in those corrugated plastic tubes Land Rover used to cover the wiring loom, and with salt on the roads at this time of year it might be shorting. The wiring on TD5s is comprised of conductors that become hard and brittle combined with insulation that gets hard too, and flakes off. Land Rover must have had a weird batch of wires from their suppliers. I've ended up fitting a whole replacement red plug loom and deal with failures in the rest of the wiring on a piecemeal basis as they come up.

Yes, of course there's the usual problems like oil in the wiring loom under the rocker cover, verdigrised earth points , fuel feed problems and much more.

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thank you, I'll have a good look at the wiring from pedal to ECU and see what I can see. If it looks like it could do with an overhaul, you might find me back here asking for more advice!

johnlad said:

Wet weather could just be coincidence. When car will tick over but won’t accelerate when pedal pressed could be a faulty throttle position sensor

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I don't get an issues at all at any other time other than in the wet, but thank you anyway and I will still have a look at the sensor.

It could be sucking in water through the air filter. Check the air filter box and there should be an outlet pipe with a valve on it to let water out, check this isn't blocked.

The trouble with these intermittent faults is that the car behaves impeccably when presented to a garage or auto electrician, yet when on a lonely road with no mobile phone signal will become more or less inoperable.

wireman said:

It could be sucking in water through the air filter. Check the air filter box and there should be an outlet pipe with a valve on it to let water out, check this isn't blocked.

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Thank you, I've checked that and all good

Brown said:

The trouble with these intermittent faults is that the car behaves impeccably when presented to a garage or auto electrician, yet when on a lonely road with no mobile phone signal will become more or less inoperable.

Click to expand...

Don't I know it!