Transient Power interruptions - D4 HSE

[Allycat]

I have had sudden engine power failures on six occasions. All forward thrust disappeared each time, including in some very compromising situations. Took me a few episides to realise I could overcome it each time by releasing the accelerator and then immediately pressing it again, and the engine would carry on as per normal.
Dealer is stumped (more likely that they didn’t actually believe me and didn’t look into it)😂 it hasn’t happened for a few months, but I’ve mostly been using my D5 recently to keep the k’s down on my beloved D4 (185k currently).

[Celtoid]

So it's different from the infamous D4 'hesitation' coming out of intersections and onto roundabouts, etc?

[Eric SDV6SE]

You'll need to plug in an OBDII code reader (Gap ID tool is the preferred) and check what error codes are present. This is what the dealer should/would have done. The vehicles ECUs log all faults and codes.

If they haven't or wont, take it to a reputable LR dealer or an independent mechanic who knows Land Rovers and has the right tools.

Eric

[DiscoJeffster]

You'll need to plug in an OBDII code reader (Gap ID tool is the preferred) and check what error codes are present. This is what the dealer should/would have done. The vehicles ECUs log all faults and codes.

If they haven't or wont, take it to a reputable LR dealer or an independent mechanic who knows Land Rovers and has the right tools.

Eric

It might not be showing a fault, so live values might also help here to show things like fuel pressures. I’m sure I’ve seen something similar related to fuel pressure issues.

[LRD414]

.... overcome it each time by releasing the accelerator and then immediately pressing it again, and the engine would carry on as per normal.
Could be throttle position sensor intermittent fault.

[Eric SDV6SE]

Could be throttle position sensor intermittent fault.

Surely something like that would be logged or cause a cascade type fault that is then logged.

Sorry, but I find it hard to believe that "live" faults are not logged.

Eric

[DiscoJeffster]

Surely something like that would be logged or cause a cascade type fault that is then logged.

Sorry, but I find it hard to believe that "live" faults are not logged.

Eric

If the engine isn’t seeing a fault, eg a sensor is misreporting, and there is no other way for it to know that sensor is at fault, it won’t necessarily report a fault.

You are generally right though that most issues trigger faults as issues generally affect multiple systems.

[Eric SDV6SE]

Thanks for that, that clarifies it for me.

[Allycat]

So it's different from the infamous D4 'hesitation' coming out of intersections and onto roundabouts, etc?

Ah yes, that lovely hesitation before she finally decides to accelerate. No it's not that. It's a very definite sudden loss of engine power, has happened whilst accelerating, and whilst cruising along at the same speed. Honestly I don't know why the Dealer never seems to have any idea. You guys on this forum should go work for Land Rover. At least problems would actually be solved, not "are you sure you aren't imagining it?"!!
Whilst they never did find the problem, it hasn't recurred for a while now. As I mostly use the D4 to tow, lets hope it never happens towing 3.5T up a hill.

[Redtail]

This happened to me - and still does happen from time to time - especially when accelerating from stationary.

It turns out my hiking boot (and another pair of shoes) are just wide enough to brush the edge of the brake pedal if I'm not careful where I put my foot. It's enough to activate the brake switch and the car thinks you actually want to stop.
I kid you not! I also saw this issue posted on the D3&4 Owners FB group, and suggested the OP check his foot position. It turned out he had in fact just bought new boots and that was the cause.

Worth checking if it's that simple.

[DiscoJeffster]

Yes. The car will not accelerate if you also press the brake. It will also log a fault code for it! I tried it once for a laugh.
It doesn’t sound like the OP’s issues though you never know

[remoman]

Could be EGR's failing.

[DiscoJeffster]

Could be EGR's failing.

Yep. Flap not closing when acceleration detected.

[Graeme]

An incorrect EGR valve position would log a fault, as should a faulty TPS because the TPS has multiple tracks for cross-checking the pedal position. A temporary loss of the crankshaft position sensor output wont normally log a fault (known cases) although why it can be overcome with throttle movement might take some close inspection of wiring harnesses for chafing to resolve. Logging live values is the key.

Edit: I knew of a TDV6 D3 whose engine would stop if reversing at other than idle. I suspected a broken wire or bad connection to the crankshaft position sensor but neither the owner nor I had the time to properly investigate. Getting stuck ascending a sand dune meant a snatch was required!