Disco 3 TDV6 Hates towing

My 2006 Discovery TDV6 SE is the best of many cars I have had but it hates towing. Put our 2 tonne caravan on the back and point it at a very short and not too steep hill and by the time we get to the top we're in creep home mode at about 20 kph. Turn off the ignition for 30 seconds, restart and all is well for 50 kilometers and another longer but shallower hill. By the top the car is getting hot, lacks power, blows black smoke, changes gears up and down almost without reason and the cruise control looses around 1kph each 15 seconds. All this on flat ground over 20 kilometers. Stop for 30 minutes and restart with nothing wrong for the next flat 50 kilometers. No fault codes or dash warnings are evident. Any suggestions or should I just scrap the car.

Wecome to LZ

Try a search on google for egr valve failure, quite common, cheap fix is blank plates which mine has had fitted for 6 years now.
Other thing which is quite common is split intercooler hoses, the favourite is the large one on the right front of the vehicle its about 2 feet long so easy to spot, even if it looks good dont be fooled, take it off and check it thoroughly, the other two much smaller and frankly arsehole to get at hoses are passnerg side and almost totally hidden.
Both of the above faults will give you lack of power and black smoke.

There are of course other possible issues, but these are the easiest to check out first.

Is it auto, if so it may have never towed previously, the auto gearbox puts the car in limp mode unless the ecu is told it has a tow bar fitted, when LR fit a tow bar it’s activated, a lot of aftermarket installations were never activated. as the ecu monitors the temperature of the gearbox oil and without knowing its towing it spots the oil temp rise for no apparent reason and reduces power.

Roger Wilson said:

Any suggestions or should I just scrap the car.

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It's a bit extreme to scrap it for a minor running issue. Surely it's best to put a diagnostic on it, to identify the issue causing reduced power?

Thanks everyone, problem is solved. We replaced the air flow meter and now it works perfectly.

Well we thought it was solved by replacing the air flow meter but the cure was only partial. The intercooler hoses are ok. and now we can get 150 km up and down hills with no problem, stopped for lunch, about 60 minutes, then 2 km from restart on reasonably flat ground, lost cruise control, black smoke at any mild acceleration, just touch the accelerator and immediately change down 2 gears. Slight temperature rise and mild loss of power. stop and turn off for 2 minutes and all is working normally for 50 km. All this while towing the 2 tonne caravan. With no van attached the car performs like brand new. No warning lights and no obvious fault codes when tested.

Roger Wilson said:

Well we thought it was solved by replacing the air flow meter but the cure was only partial. The intercooler hoses are ok. and now we can get 150 km up and down hills with no problem, stopped for lunch, about 60 minutes, then 2 km from restart on reasonably flat ground, lost cruise control, black smoke at any mild acceleration, just touch the accelerator and immediately change down 2 gears. Slight temperature rise and mild loss of power. stop and turn off for 2 minutes and all is working normally for 50 km. All this while towing the 2 tonne caravan. With no van attached the car performs like brand new. No warning lights and no obvious fault codes when tested.

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Any codes?

No codes.

Hi

plus 1 what’s already been mentioned plus looking at the code readers live data will also assist

ref the sensor was it the MAF or MAP sensor u replaced plse,

Have u had chance with the other intercooler hoses down by the turbo, indeed the left hand side one as u look at the engine is a favourite for splitting , only true way is to remove it and bend the corner as a split can be hidden on the underside of the hose

has the oil level been checked inside the gearbox

know it can be frustrating but think I can speak for all of us that own D3 that with a multimeter and a code reader can slowly work through it stage by stage

also have u checked what the low fuel pressure is and when the fuel filter was changed, but that would normally bring a fault code up

Strange there’s no warnings or limp mode , may i ask what code reader ur using plse , is it a gerenic one

I’m wondering if the Map sensor is blocked and a split or loose intercooler hose because of the black smoke

ur find this forum extremely helpful and plenty of us to help , so as u test things and let us know we can assist in where to go next

hope that helps a little

lynall said:

Wecome to LZ

Try a search on google for egr valve failure, quite common, cheap fix is blank plates which mine has had fitted for 6 years now.
Other thing which is quite common is split intercooler hoses, the favourite is the large one on the right front of the vehicle its about 2 feet long so easy to spot, even if it looks good dont be fooled, take it off and check it thoroughly, the other two much smaller and frankly arsehole to get at hoses are passnerg side and almost totally hidden.
Both of the above faults will give you lack of power and black smoke.

There are of course other possible issues, but these are the easiest to check out first.

Click to expand...

hiya

ur so right about the *##***#**# hoses down by the turbo, when I replaced mine with silicone ones I thought the designer needs bloody shooting , lol

know when I had a broken intercooler clip by the turbo I had a code error , plus seen some pics of the left hand long intercooler splits , see u have to bend the hose back before noticing them

also wonder if the Map sensor is blocked , thought about fuel filter but that would bring a fault code up

Ah, the joys of fault finding , lol

johnlad said:

Is it auto, if so it may have never towed previously, the auto gearbox puts the car in limp mode unless the ecu is told it has a tow bar fitted, when LR fit a tow bar it’s activated, a lot of aftermarket installations were never activated. as the ecu monitors the temperature of the gearbox oil and without knowing its towing it spots the oil temp rise for no apparent reason and reduces power.

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hiya

u says that there was one a while ago, oil level was low along with dexron being used

something else I found out is I couldn't believe how many systems go through the ABS module

Nodge68 said:

It's a bit extreme to scrap it for a minor running issue. Surely it's best to put a diagnostic on it, to identify the issue causing reduced power?

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think we’ve all done a basil fawlty on these, lol

Thanks for all these replies. In rough order, not sure which sensor was replaced, it is the one at the front large about 4 or 5 inch diameter. Not at home so can't check the invoice. Was replaced by my very trusted specialist LR authorised service centre. Same workshop checked the hoses and used their code reader. Transmission oil has been fully drained and replaced with new base plate and filter without any change. I am aware of a sluggish injector on number 5 cylinder due for replacement at a service next month. The really great mystery is that when not towing the car performs like a brand new vehicle. Today I drove 200 km on country roads and could not fault its performance. Going to follow up all the other suggestions in your very valued replies, thanks again.

Roger Wilson said:

Thanks for all these replies. In rough order, not sure which sensor was replaced, it is the one at the front large about 4 or 5 inch diameter. Not at home so can't check the invoice. Was replaced by my very trusted specialist LR authorised service centre. Same workshop checked the hoses and used their code reader. Transmission oil has been fully drained and replaced with new base plate and filter without any change. I am aware of a sluggish injector on number 5 cylinder due for replacement at a service next month. The really great mystery is that when not towing the car performs like a brand new vehicle. Today I drove 200 km on country roads and could not fault its performance. Going to follow up all the other suggestions in your very valued replies, thanks again.

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hi

Ur so welcome and always a team effort

that sounds like ur Maf , get them to check the Map sensor that sits in ur throttle body

Another suggestion ref @johnlad , make sure the CCF files within diagnostics have been changed for towing

as there Lr specialists they should have the correct diagnostics to pin it down for u , maybe hook up ur caravan and then let them sit in the vehicle whilst ur driving and they can live scan the system to see what changes

hope that helps and indeed Plse let us know how u get on

You tow a 2 tonne caravan at 150km/hr????

flat said:

You tow a 2 tonne caravan at 150km/hr????

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Never been over 95 kph and usually a lot less

Roger Wilson said:

Well we thought it was solved by replacing the air flow meter but the cure was only partial. The intercooler hoses are ok. and now we can get 150 km up and down hills with no problem, stopped for lunch, about 60 minutes, then 2 km from restart on reasonably flat ground, lost cruise control, black smoke at any mild acceleration, just touch the accelerator and immediately change down 2 gears. Slight temperature rise and mild loss of power. stop and turn off for 2 minutes and all is working normally for 50 km. All this while towing the 2 tonne caravan. With no van attached the car performs like brand new. No warning lights and no obvious fault codes when tested.

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Oh I just re-read your post and do you mean ‘150km DISTANCE?’

I took it as you thrash about every where at 150km/hr lol

flat said:

Oh I just re-read your post and do you mean ‘150km DISTANCE?’

I took it as you thrash about every where at 150km/hr lol

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must admit I read it for speed as well

flat said:

Oh I just re-read your post and do you mean ‘150km DISTANCE?’

I took it as you thrash about every where at 150km/hr lol

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Just reread it myself and you're right, I was not at all clear, meant 150 km distance which was done at an average 90 kph, sorry for my bad writing.

Roger Wilson said:

Just reread it myself and you're right, I was not at all clear, meant 150 km distance which was done at an average 90 kph, sorry for my bad writing.

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It is no worries I was just going to say slow down and see if it makes a difference