Disco 3 (LR3) Down on power, no fault codes. Where to look next?

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Martin Radoczi

Martin Radoczi

Active Member
Posts
79
Location
Royston, Hertfordshire
I’ve got an ‘05 D3 TDV6 which I’m preparing for overland use (it was on the front cover of LRO a couple of months ago. It’s wanted for nothing, and has been faultless in the 4 years I’ve owned it, but I’ve done loads of preventative maintenance.

Just come back from a week around Northumberland and Scottish Borders (it was meant to be The Alps for two weeks, but I got COVID the day before we were meant to leave :censored:

Whist away, I was losing a lot of speed and struggling up some hills - I thought it was just me driving like a driving instructor, and trying to move a vehicle whose weight has increased somewhat from standard with all the kit I carry etc.

Plugged in the GAP tool, and got “P0299 - turbo underboost.”

A couple of weeks ago I was getting a noticeable whistle through the raised air intake, sounding very much like a police siren, but that has stopped now.

My local indie had it for a pre-Alps inspection, and noticed the tube actuator was a bit sticky, so they freed that up.

I can confirm that the actuator seems to be moving freely enough.

I have always stayed on top of keeping MAP and MAF sensors clean, but changed the MAP anyway this week.

I am trying to be methodical in tracking down the cause of my issue, before replacing the turbo (which I’m not overly happy about, but have no problem doing it if necessary!) but I only have a limited mechanical knowledge.

I have ZERO lights on the dashboard, no restricted performance, or anything to suggest it wasn’t running beautifully, until I try to get up to speed - I couldn’t get over 55mph on a run between roundabouts on a dual carriageway, where it’s easily hit 90 before.

So far this week, I have:

- changed the fuel filter in case it was partly blocked/connections were on wrong.
- changed the MAP sensor.
- changed the 3 seals on the throttle body.
- used contact cleaner to clean the MAF sensor.

On Sunday I will replace the intercooler and ensure that all the silicone hoses I have fitted are all still intact, and the hose clips robust etc
The only one of the hoses that are still original, is that little one that a PITA to change near the turbo.

After changing the fuel filter today, I cleared any fault codes, took it for a spirited drive around town, and it *seems* slightly better, but now I have absolutely NO fault codes at all, but it’s still nowhere near perfect.

Before I have the turbo replaced, does anyone have any suggestions of things that I can check and look for first? Or any sort of advice?
 
My advice is:
don't spend money unless you know it is necessary!
But then I am tight!
It's easy enough to check out a turbo.
And why do you think it might be that?
Have you tried simply unplugging the MAF?
Anyway, @gstuart knows far more about your particular Disco than I do, hopefully he'll come on.;)
 
This is PRECISELY why in posting here! I don’t want to fit a new turbo if it’s not necessary, but I’m just trying to work out if there’s anything I might have missed that I could check!

MAF has been unplugged several times! Is there a test to see if it’s working correctly? The little wire inside is intact, and looks clean enough.
 
Martin Radoczi said:
This is PRECISELY why in posting here! I don’t want to fit a new turbo if it’s not necessary, but I’m just trying to work out if there’s anything I might have missed that I could check!

MAF has been unplugged several times! Is there a test to see if it’s working correctly? The little wire inside is intact, and looks clean enough.
Click to expand...
MAFs are funny buggres. They can look OK and still be fubar. Unplugging it and no difference, chances are it is OK, but a decent diagnostic will tell you if it's not right. My Foxwell does. Contact cleaner isn't necessarily the best stuff to clean it with, better off using sensor cleaner as many contact cleaners leave a coating on whatever you use it on.:eek:
As I said, hopefully someone else will come on to help.
Have you done a live data recording? that will tell us a lot, or should.;)
I recently used it to diagnose that my MAP/IAT was up the spout. (Twas the IAT side that was wrong, it was perfectly clean that made no difference!) (I have a D2 TD5.)
 
Start with basics, people always says its the turbo or something else equally expensive.
Remember not enough fuel = not a lot of go, lack of air or turbo sulking would normally give you excess smoke.

Air filter good? whistling noise would make me suspect something has collapsed inside or some other foreign debris has gotten in there, dont forget the trunking inside the drivers side wing is a crap fit even when its good.
Large intercooler hose good? just because its silicone does not mean it cannot fail, though mine is 7 odd yrs old and still good.
Fuel supply good? take a look on the D3forum as there is a proper guide on how to check it out.

Got a diag tool so you can read live on the road data? ie boost pressure, fuel rail pressure etc etc.
 
Yep, that’s exactly what I’m doing - starting where air enters the vehicle, and checking every step up to the turbo.

Even though my MAF sensor *looks* okay, I’ve ordered another one just in case. Will fit that when it arrives next week.

Today, I managed to get as far as replacing the little hose near the turbo. I’ve disconnected the hose on the left of the intercooler (not the main hose) and both it, and the hose clips all looked good.

Tomorrow I’ll swap out the intercooler, and inspect the main IC hose and it’s clips.

The air filter is an ITG performance foam filter, and it was recently cleaned and oiled. Is it possible that over-oiling it could be restricting air intake? My gut reaction is unlikely.

Even though I did it before my aborted Alps trip, I changed the fuel filter again, fearing it was partially blocked, or the 4 connectors were on wrong. The filter is an OEM Delphi filter and the connections are 100% correct.

I was really hoping that when I had a good view of the intercooler, I’d see obvious signs of leakage, but disappointed to see nothing on the passenger side at least.

I’m not overly comfortable with reading live data with my GAP tool - if I’m honest, I don’t really know what I’m looking at, and how to interpret it.
 
Martin Radoczi said:
Yep, that’s exactly what I’m doing - starting where air enters the vehicle, and checking every step up to the turbo.

Even though my MAF sensor *looks* okay, I’ve ordered another one just in case. Will fit that when it arrives next week.

Today, I managed to get as far as replacing the little hose near the turbo. I’ve disconnected the hose on the left of the intercooler (not the main hose) and both it, and the hose clips all looked good.

Tomorrow I’ll swap out the intercooler, and inspect the main IC hose and it’s clips.

The air filter is an ITG performance foam filter, and it was recently cleaned and oiled. Is it possible that over-oiling it could be restricting air intake? My gut reaction is unlikely.

Even though I did it before my aborted Alps trip, I changed the fuel filter again, fearing it was partially blocked, or the 4 connectors were on wrong. The filter is an OEM Delphi filter and the connections are 100% correct.

I was really hoping that when I had a good view of the intercooler, I’d see obvious signs of leakage, but disappointed to see nothing on the passenger side at least.

I’m not overly comfortable with reading live data with my GAP tool - if I’m honest, I don’t really know what I’m looking at, and how to interpret it.
Click to expand...

I think people try and make it sound really complicated, but all you want to know is the simple things like boost pressure/temps and so on, even better if you have another D3 to try and compare readings to, basically anything out of the ordinary, throttle reading 100 percent when you floor it, external temp sensor reading/coolant and oil temps.
Is the seal good where the large plastic top inlet pipe joins the vertical intake pipe just under/behind the two oil cooler rubber hoses?
I would try a new std filter and clean the maf, maf can be checked with live data even just idling, air intake temp can also be checked with the Gap, if you google hot wire maf you will find why oil mist can mess up the readings

Only thing I will say is if playing with the Gap for more than 10 mins you will need to hook up a charger to keep battery healthy.

Cannot offer any more data comparisons as car is in the shop having auto box repaired, first time in 8 yrs it has someone else lay spanners on it.
 
Martin Radoczi said:
The only one of the hoses that are still original, is that little one that a PITA to change near the turbo.
Click to expand...

You know that's the most likely boost hose to fail don't you?

Martin Radoczi said:
I’m not overly comfortable with reading live data with my GAP tool - if I’m honest, I don’t really know what I’m looking at, and how to interpret it.
Click to expand...

The IID is easy to use, and as long as you're only reading data, you can't do any harm. ;)
 
lynall said:
Not on the D3, the large main intercooler hose is the first to fail, the two smaller hoses are tough little cookies.
Click to expand...
It failed on mine, and on a friends D3 too, and they're a PITA to change.
A low boost code does suggest a boost leak though.
 
Thanks for the replies so far, gentlemen.

Right, so today I have done the following:

- replaced the little hose near the turbo. Old one was still fine, as were the hose clips. Not a job I’m in any rush to do again!
- changed the intercooler. Some of the fins were a all bent, but no obvious sign of anything major wrong with the old one.
- disconnected and inspected the other two IC hoses. All good, as were the hose clips.
- checked yet again that the turbo actuator is moving freely. Key in ignition to position 2, and the actuator cycles freely back and forth.

Started it up, and it was initially a bit sluggish. Remembered to clear faults, and started again, and it can only rev to 4000rpm.

Checked fault codes again, and it’s coming up with a MAP fault (didn’t get to note the exact code, as it started tipping down, and I was getting fed up!)

It’s a new MAP sensor, so could this suggest and electrical connection fault?

I did quickly look at some live data, and MAP was showing 96kpa, with external about 95, which I believe is about right?
 
Martin Radoczi said:
I did quickly look at some live data, and MAP was showing 96kpa, with external about 95, which I believe is about right?
Click to expand...

100 kPa is atmospheric pressure, so 95 kPa is under atmospheric pressure, which on a boosted engine shouldn't happen, unless the throttle plate is closed.
 
Martin Radoczi said:
Thanks for the replies so far, gentlemen.

Right, so today I have done the following:

- replaced the little hose near the turbo. Old one was still fine, as were the hose clips. Not a job I’m in any rush to do again!
- changed the intercooler. Some of the fins were a all bent, but no obvious sign of anything major wrong with the old one.
- disconnected and inspected the other two IC hoses. All good, as were the hose clips.
- checked yet again that the turbo actuator is moving freely. Key in ignition to position 2, and the actuator cycles freely back and forth.

Started it up, and it was initially a bit sluggish. Remembered to clear faults, and started again, and it can only rev to 4000rpm.

Checked fault codes again, and it’s coming up with a MAP fault (didn’t get to note the exact code, as it started tipping down, and I was getting fed up!)

It’s a new MAP sensor, so could this suggest and electrical connection fault?

I did quickly look at some live data, and MAP was showing 96kpa, with external about 95, which I believe is about right?
Click to expand...

I have noticed on my D3 that a lot of the conduit on the engine loom is breaking up and literally falling off, and I thought some of the wires are going to be an issue as the car gets older.
Lot of cars will not give you full rpm at a standstill.
Have you still got the old map sensor? might pay to compare it to the new one.

Maybe block one port of the old cooler and then fill it with water to see it if holds the fluid?
 
Martin Radoczi said:
I’ve got an ‘05 D3 TDV6 which I’m preparing for overland use (it was on the front cover of LRO a couple of months ago. It’s wanted for nothing, and has been faultless in the 4 years I’ve owned it, but I’ve done loads of preventative maintenance.

Just come back from a week around Northumberland and Scottish Borders (it was meant to be The Alps for two weeks, but I got COVID the day before we were meant to leave :censored:

Whist away, I was losing a lot of speed and struggling up some hills - I thought it was just me driving like a driving instructor, and trying to move a vehicle whose weight has increased somewhat from standard with all the kit I carry etc.

Plugged in the GAP tool, and got “P0299 - turbo underboost.”

A couple of weeks ago I was getting a noticeable whistle through the raised air intake, sounding very much like a police siren, but that has stopped now.

My local indie had it for a pre-Alps inspection, and noticed the tube actuator was a bit sticky, so they freed that up.

I can confirm that the actuator seems to be moving freely enough.

I have always stayed on top of keeping MAP and MAF sensors clean, but changed the MAP anyway this week.

I am trying to be methodical in tracking down the cause of my issue, before replacing the turbo (which I’m not overly happy about, but have no problem doing it if necessary!) but I only have a limited mechanical knowledge.

I have ZERO lights on the dashboard, no restricted performance, or anything to suggest it wasn’t running beautifully, until I try to get up to speed - I couldn’t get over 55mph on a run between roundabouts on a dual carriageway, where it’s easily hit 90 before.

So far this week, I have:

- changed the fuel filter in case it was partly blocked/connections were on wrong.
- changed the MAP sensor.
- changed the 3 seals on the throttle body.
- used contact cleaner to clean the MAF sensor.

On Sunday I will replace the intercooler and ensure that all the silicone hoses I have fitted are all still intact, and the hose clips robust etc
The only one of the hoses that are still original, is that little one that a PITA to change near the turbo.

After changing the fuel filter today, I cleared any fault codes, took it for a spirited drive around town, and it *seems* slightly better, but now I have absolutely NO fault codes at all, but it’s still nowhere near perfect.

Before I have the turbo replaced, does anyone have any suggestions of things that I can check and look for first? Or any sort of advice?
Click to expand...

hi

u have my sympathy as I’ve recently replaced all my intercooler hoses with silicone ones along with t bolt clamps , indeed very fiddly to say the least to replace , had a nightmare with mine as when I hit 55mph it would vibrate, along with loss of power but mine would go into limp mode

After a drive plse check ur brake discs to see if there hot

on live data plse check ur Boost pressure adjustment - bank O, cycle the ignition key on and off and ur see the % change , please let us know what the lowest and highest readings are , thks

Used a smoke machine on mine and found air leaks at the throttle body where the egr pipes were fitted , mine are also blanked , have u still got ur pipes fitted and where are they blanked plse

Really hope that also helps a little as understand it can be very frustrating trying to pinpoint the fault , have a few other tests u can do but just wish to see what reading u get back first , thks

Ps, before I forgot , don’t wish to try and teach u how to suck eggs but when u fitted new intercooler hoses , did u also check the air inlet pipe clamp that fits onto the turbo plse, thks

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E5043DCA-C7BD-4227-9470-7BCFC1D6ADD7.jpeg
F5232DCA-36E5-4249-98B6-A73ED36FDA8F.jpeg
 
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