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D2 TD5 struggling under load


reb78

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My D2 has had an intermittent issue for a while where it cuts out briefly at 4250rpm accelerating hard in 3rd and then continues to accelerate. As i said, it was intermittent and I rarely rev it that hard anyway.

Hitched the horse trailer up today to go to SWMBOs for the Christmas break so the car was loaded and had the trailer on the back (albeit empty). On the way up to the yard, I noticed a bit of hesitation and poor acceleration when i put my foot down - I didn't remember it being like that last time i towed (even with horses) but thought it was just the trailer jerking on the back of the truck. A mile or so later, it became obvious it was a similar problem to above - most obvious this time with a jerky/kangaroo at about 3500rpm accelerating in 2nd (no horses otherwise I wouldn't have been playing around like that!).

Any ideas?? - wastegate moves freely (mole grips on the shaft I can move it smoothly as far back and forth as the actuator allows). The little vacuum pipes look ok, but are as old as the car by the look of them - so could these be the cause if there is a leak in them that I cant see? Do the boost modulators on these commonly fail?

(EGR is removed, MAF is probably two years old VDO/Siemens unit if either of these make any difference)

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I don't have much to offer here I'm afraid - but the first thing everyone always seems to say is check the loom ?

When oil reached my ECU is did odd things like that - and they seemed to increase in frequency the more oil there was.

You can rule out the MAF by just disconnecting it - so it falls back to the ECU default setting.

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When you say mole grips on the wastegate do you need to use the molegrips? In my experience, when they're free you can just flick them by hand.

That's with the actuator still connected, otherwise I agree, it would be way too stiff.

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Hmmm. I wonder if it is injector washers. Would they really be this intermittent? The cut out at 4250rpm has been there for a couple of years and not worsened. No problems with oil level ever. I need to check it now, but it's not parked on a level area at the in laws, so I can't check it for the next few days.

I don't know if this is related, but today, the other half went to start the car it cranked fine, caught for a second then stalled. Did this again, then I said to try cranking it for a second longer, it started, rough for 5 secs and grey smoke, then ran fine.

Any more ideas? I need to hook the nanocom up, but don't have it with me.

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So, popped out today. Checked the oil and water (it is on a fair slope so this won't be too accurate) there is oil in there just above max and the coolant seemed a little low (10mm below the cold fill mark). Then started it and it did the same thing again. Grumbled, wouldn't start, a second time, grumbled wouldn't start and then third time it started. Grey smoke again from the exhaust. Video below if the upload works

trim.3A11C4B4-B7C0-47C1-80B0-9058577AF2F4.MOV

Took it out and as I pulled up the road, I had a lot of smoke, then it cleared and ran fine, except for when I put my foot down and then I had the kangaroo, hesitation whenever it was under load (even light ish load), not just at high revs this time. I'm my desperation and in the absence of my nanocom, I unplugged the MAF just to see what it would do. No kangaroo, no hesitation and pretty much back to normal. Slightly sluggish on the first pull away after starting with the MAF disconnected, but it's like the ECU needed to realise the MAF was unplugged and once it did, it behaved for the rest of the journey! Pulled away well, no hesitation under load and could rev right to 4500rpm if I wanted. Won't know till tomorrow if this is anything to do with the starting problems.

Does it sound like the rough running is a MAF issue, or has unplugging it forced the ECU to use default MAF settings and masked something else? I don't know of it's related to the poor starting too?

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At cranking RPM the airflow through the MAF is so low as not to produce a sane signal.

When the injector-washers went on my 90 they caused progressively-longer cranking times [doing a couple of fuel system purge-cycles before trying to start would make it stutteringly fire up with only a few tens of seconds of actual cranking]. The leaky washers also led to lethargic acceleration/kangarooing throughout the rev-range, the misfire being more noticeable when hoofing it - I'm guessing that the higher cylinder combustion-pressures when using wide-open-throttle-and-waiting-for-the-rev-limiter were pushing more combustion gasses past the leaky copper washers and causing the Diesel feed to the injectors to have lots more air-bubbles in it.

A new set of copper washers and injector seals are a cheap try-it-and-see-if-it-makes-the-problem-go-away option.

The other thing I had with my TD5 was the wastegate being sticky: if it stuck open you got sloth-on-valium performance; if it stuck closed it went like a rocket until the ECU decided there'd been too-much-boost-for-too-long and then it switched back to sloth-mode. A good degree of wiggling of the wastegate actuator solved this. *DO NOT* try using oils or WD40 on the wastegate-spindle - these might free things off initially but turbo-heat carbonises the oily component and makes the mechanism much more sticky in future. If you must clean the wastegate-spindle I recommend using Isopropyl Alcohol [iPA] and then blasting it clean with an airline.

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So would unplugging the MAF mask an injector seal problem? Or do you think I have two problems here?

I've no issue changing the seals and what you say makes sense, but I'm just trying to understand why performance was improved this afternoon by unplugging the MAF.

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When I had the injector-seal and sticky-wastegate issues unplugging the MAF made no real difference. My understanding is that the MAF signal is only used to 'trim' the injection timing/volume parameters - if there's an underlying major issue the MAF-supplied fine-adjustment signal won't be able to correct for this.

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Well, started first time this morning. MAF still disconnected and snow on the ground. Curious.

Seemed a little smokier than I'd expect, but I wouldn't notice it if I wasn't looking and cleared completely after a couple of minutes.

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I'd be really interested too, 'cause I have a nanocom and a MAF but no idea what I should look for in the readings.

EDIT: scratch that, I went looking and found this thread with a great explanation from Ian - http://forums.lr4x4.com/index.php?showtopic=61385&hl=%2Bmass+%2Bair+%2Bflow+%2Bsensor+%2Boem#entry534862

Does anyone know where he is? I've been trying to message him as I owe him an ECU, but his inbox is full.

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  • 2 weeks later...

Popped out today and finally hooked up the nanocom with the MAF reconnected. MAF readings are exactly as described in the thread that Shackleton links to above:

4 with engine turned off,

62ish at idle

and will run right up to 600ish under full load.

BUT, with the MAF plugged back in the hunting under load returns (cant assess poor start as it had already been ran). Only fault logged AFTER a run was

(3,7) AIR FLOW CIRCUIT, (LOGGED HIGH)

but, i had been booting it around to see what the settings did, and have read this can be brought on by 'spirited' use of the accelerator pedal (is that true?).

Any thoughts? I take on board the comments re injector seals, wastegate modulator and the three small modulator pipes etc, but cant fathom why unplugging the MAF would remove the fault?

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I've got a file of the fuel input paramenters whilst on a run, but i cant upload it on here and dont really know how to read it.

Mods - any chance you can allow .csv or better still .xlsx files to be uploaded so we can share these outputs?

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  • 1 month later...

So, still got this problem. Its kind of been on hold whilst i fixed the starting stalling problem (that turned out to be injector seals). But this hesitation under load remains. Its been identified that the MAF reading is reaching just over 670kpa and then cutting to 0kpa. This is when the hesitation and cut in power occurs.

MAP sensor is clean

DCV has been replaced

Injector seals done

Wastegate seems free if i activate it using my compressor and a pipe.

Anyone come across this and have any ideas. The D2 is not mapped to my knowledge.

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I had been wondering that too Neil. Given the price of genuine, I think this would be ok?

http://www.island-4x4.co.uk/flow-sensor-mhk100620g-p-3943.html

I assume that's the same as LR, but in the VDO/Siemens packet?

With the MAF unplugged, I get no driving fault and it drives really well. I'm half tempted to just leave it unplugged as depending where you read, it only seems to have a major effect on the egr (which is not present on my truck).

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If unplugging it fixes the problem - then it's definitley the maf.

On my last 90 the maf was broken when I got it - but I didn't find out for a long time - and it's replacement only made incremental inprovements to the drive.

Well, that's what i thought, but when i think about it I'm not sure. Unplugging it means that it cant read the airflow and so airflow may reach this high point (and beyond) but it doesn't know as its using default figures.

Its also done this on two separate MAFs now - same problem on the last MAF and also on this one. Thing is, i cant remember if replacing the MAF last time solved the issue albeit for a brief period. I don't think it did.

I was reading this last night: http://www.irbdevelopments.com/dual_channel.html

It describes the symptoms well, but i'm pretty sure mine isn't tuned so it doesn't make any sense that it is doing it. All i want is standard performance in standard form so i should have no need for magical boxes etc!

I'm going to my parents this weekend. I think i might bring mums D2 back and start sensor swapping as hers runs fine - that way i can troubleshoot mine for no cost!

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