Disco 2 Sudden power loss on motorway; how do I go about diagnosing?

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Naf623

Active Member
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283
Location
York
Driving down to London yesterday, 73 on cruise control, when I deactivated and pressed the accelerator I got almost no response. Engine was running, car was still moving more than a coast, but slowing down. Pulled over, ignition off, cloud of smoke (white/grey, one thought it looked a bit blue, I think; smelled like TCP). Started back up and all seemed fine again, made it to London.
Driving back it did it again. One time it recovered itself while still driving, another it had me on the hard shoulder again. Some advice from a friend (aside from getting recovery - yes I know I probably should have) and we reckoned a turbo pipe had come loose. Tried sticking below 2k rpm, and it only happened once more - on the cruise control up a hill, where I imagine the turbo still kicked in. From there kept CC off, and revs low manually, and made it home (150 miles - 3 hours) without further incident.

Now I need to work out what's going on. I've had a general look around the engine bay from the top and nothing appears out of the ordinary that I've noticed.

Symptoms:
- temperature is stable (based on the needle, which I know is poor - but it never got hot enough to make that rise up)
- smoke smelled (to me) like TCP
- idling engine sounds normal (to my, granted relatively inexperienced, ear)
- smoke only occurs during power loss incidents, not when idling or any other driving, even over 2k rpm until the issue occurs.
- problem didn't occur immediately after topping 2k revs, I was happily driving well over that for some time before it occurred. It also occurred once below that, but with the cruise control up a hill, so still under extra load.
- It didn't seem like coolant or oil had dropped; but checking this morning I have to admit there's a possibility I might have lost some oil, hard to be certain; and perhaps a sliver of coolant - again hard to say for sure.

Help!

ETA:
Someone recommended giving the radiator hose (top hose?) a squeeze while someone revs it. Didn't feel any pressure or stiffening of it when revving to about 2.5k rpm.
 
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Fuel pump would be a good place to start, fault can be intermitend before it goes completly. Nanocom will be good as well.

I know it doesn't necessarily mean its fine; but it's had a brand new fuel pump less than 20k miles ago.

EDIT: checked and its only 12k miles ago, even.
 
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Hoses can also delaminate.

Of all the options so far, this is what I'm hoping it is has happened to one of the turbo hoses, and not something much worse (like a cracked head, which one person has been convinced about so far)
 
Well, I've had hoses off the turbo, and nothing relevant seems amiss. Sure the intercooler hose is past it and a little delaminated inside, but not split, so I can't see that being the problem here, as that's the pressurised side, right?
Turbo wheel has no play, though that smear on the edge seems a bit odd.
Clearly some oil leaking down the side somewhere, but not an obvious torrent.



Neighbour (a mechanic) reckons it's the MAF (partly on the basis I don't have to wait for anything to cool off - I can just turn off and on again and it seems fine again for a while); I guess I need a Nanocom to be able to test that?

Follow the first suspicion... check all the turbo/intercooler hoses, the EGR is bypassed?

Yes, EGR is bypassed.

Big immediate question is what else do I need to check to make sure it's safe to drive (locally, calmly) without causing further damage?
 
Neighbour (a mechanic) reckons it's the MAF (partly on the basis I don't have to wait for anything to cool off - I can just turn off and on again and it seems fine again for a while); I guess I need a Nanocom to be able to test that?
You dont need nanocom just for the MAF but you need one to see what happens in reality. To rule out the MAF it's enough to unplug it and drive it so and if it goes well then you need a new one but only if it's Eu3 engine , if it's Eu2 the MAF would not cause any noticeable driveability issues if the EGR is bypassed. If you ruled out a boost leak the symptom you described
smoke only occurs during power loss incidents, not when idling or any other driving, even over 2k rpm until the issue occurs
can be caused by the MAP/IAT or the AAP(airbox) sensor and for these you need a diag tool or to replace it with 100% good one to rule it out,.... IMO as long as smoke is involved it's something boost related or injection issue but that's not very common. Did you check for oil in the ECU red plug?.... and check te air filter too
 
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You dont need nanocom just for the MAF but you need one to see what happens in reality. To rule out the MAF it's enough to unplug it and drive it so and if it goes well then you need a new one but only if it's Eu3 engine , if it's Eu2 the MAF would not cause any noticeable driveability issues if the EGR is bypassed. If you ruled out a boost leak the symptom you described

How do I know if it's EU2 or EU3? Is there anything more serious it could be, which going for a drive would be bad for?
I'm looking at maybe getting an iCarsoft LR V2 so I at least have something I can read codes with.


can be caused by the MAP/IAT or the AAP(airbox) sensor and for these you need a diag tool or to replace it with 100% good one to rule it out,.... IMO as long as smoke is involved it's something boost related or injection issue but that's not very common. Did you check for oil in the ECU red plug?.... and check te air filter too

Air filter is good, changed just before Christmas (which has annoyed me, because I'd put a washable performance one in there, and that's vanished). I tried my best to clean out the ECU plugs a few months back; a full can of cleaner on each. Still not confident it fully cleaned them, so I suppose that's a possibility.
 
How do I know if it's EU2 or EU3?
from what year is the engine? usually facelifts are Eu3 and non-facelifts Eu2 except some 2002 "transition" non-facelift modells which can be Eu2 or 3 or a kind of 2/3 hybrid depending on VIN.
I tried my best to clean out the ECU plugs a few months back; a full can of cleaner on each
If there was oil in the red plug you have to replace the injector loom ASAP with genuine LR to be OK cos the injection is mixed up, cleaning the oil has almost the same effect like massage to a prosthetic leg cos the contacts in that circuit are weak
I'm looking at maybe getting an iCarsoft LR V2 so I at least have something I can read codes with.
You can't rely on Td5 engine management codes retrieved with that tool whatsoever, maybe for some live data readings but that's not sure either, all you can know for sure is that there are no codes at all but once a code is present that tool can missread it or even report non-existent codes, i know, i had one myself
.
 
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from what year is the engine? usually facelifts are Eu3 and non-facelifts Eu2 except some 2002 "transition" non-facelift modells which can be Eu2 or 3 or a kind of 2/3 hybrid depending on VIN.

It's from 2001, so should be EU2. It's been remapped and they didn't have to replace the chip, though; which I thought was a later thing.


If there was oil in the red plug you have to replace the injector loom ASAP with genuine LR to be OK cos the injection is mixed up, cleaning the oil has almost the same effect like massage to a prosthetic leg cos the contacts in that circuit are weak

That seems extreme; I've never heard anyone say more than give them a good clean out.

You can't rely on Td5 engine management codes retrieved with that tool whatsoever, maybe for some live data readings but that's not sure either, all you can know for sure is that there are no codes at all but once a code is present that tool can missread it or even report non-existent codes, i know, i had one myself

So it's Nanocom or bust, then?
 
That seems extreme; I've never heard anyone say more than give them a good clean out.
seems that you didnt dig enough in this area then or you spoke with the wrong people, It's not extreme at all and the only real cure for that believe me.
So it's Nanocom or bust, then?
For reliable Td5 engine management diagnostics the cheapest versions are nanocm or hawkeye.... it was Lynx too but became obsolete afaik
 
seems that you didnt dig enough in this area then or you spoke with the wrong people, It's not extreme at all and the only real cure for that believe me.

The idea of removing the rocker cover makes me nervous haha. I'm sure its fine, I've just not gone there before.

OK, so I'll have to get it to the garage to get the codes read. Is checking them, then clearing them, then trying to cause the issue again necessary?
What should I be checking first to try and make sure it's safe to drive and not going to cause any more serious damage, as long as I'm careful?
 
seems that you didnt dig enough in this area then or you spoke with the wrong people, It's not extreme at all and the only real cure for that believe me.
For reliable Td5 engine management diagnostics the cheapest versions are nanocm or hawkeye.... it was Lynx too but became obsolete afaik
Does this mean that you don't rate the Foxwell for engine management diagnostics?
 
Does this mean that you don't rate the Foxwell for engine management diagnostics?
Not anymore, i was happy with it at the beginning but after it gave me a strange not Td5 specific fault code once i cross tested it with Hawkeye and realised it's not 100% accurate even though it's a bit better than iCarsoft it can be erratic on EMS codes but smarter for the rest of the systems. At this point seems the cheapest and most reliable alternative for nanocom or hawkeye with some slight glitches when it comes to EMS fault codes.
 
Not anymore, i was happy with it at the beginning but after it gave me a strange not Td5 specific fault code once i cross tested it with Hawkeye and realised it's not 100% accurate even though it's a bit better than iCarsoft it can be erratic on EMS codes but smarter for the rest of the systems. At this point seems the cheapest and most reliable alternative for nanocom or hawkeye with some slight glitches when it comes to EMS fault codes.

I assume the diagnostic systems that established garages have will read them fine? It's not like Nanocom and Hawkeye are the only viable options - just the cheapest consumer-ish ones?
 
Depends on the tool, generic multivehicle ones based on OBD2 protocol are not OK unless they have the specific LR software loaded and these are all above 5000 GBP. As long as your air intake is not clogged and the turbo hoses are all good i dont see what you can check more without diagnostics but if the ECU red plug was once full of oil and not replaced with new you have to rule this out first, only genuine LR is acceptable, aftermarkets can fail in no time, it's pure lottery
 
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