Hooray, my soot problems are back (unfortunately)!

This problem seems to have appeared over the last week.

The car is now producing black soot all the time - a very fine mist of black soot when cruising and it is now billowing a large quantity of soot no matter what level of acceleration. This is through both exhausts.

Finally however, a fault code has appeared on the engine ECU, which gives a starting point because, it seems to coincide:

P023D-22 (2F) Manifold absolute pressure - turbocharger/supercharger boost sensor A correlation - General signal failure - signal amplitude>maximum

The manual says:

Intake air systemfault
Turbochargermechanical fault - see point above
Intake airtemperature (IAT)sensor fault - see point below
Mass air flow (MAF)sensor fault - see point below
Manifold absolutepressure andtemperature (MAPT)sensor fault - these are reading normal and within a small tolerance of each other
Exhaust gasrecirculation (EGR)sensor fault - this reads normal but, I'm suspicious given the amount of soot and that these engines are known for EGR issues.
Turbochargeractuator positionsensor fault - these are reading normal and within a small tolerance of each other

Check the intake air system. Check the turbochargermechanical condition and operation. Check for DTCsindicating a listed sensor fault. Rectify as necessary.Using a datalogger function, monitor the turbochargeractuator position and command the actuator to 5%PWM, then 95% PWM in 5% steps. Check the results.There should be a smooth curve between theminimum and maximum values. If not, install a newturbocharger.REFER to: Turbocharger RH (303-04D Fuel Chargingand Controls - Turbocharger, Removal andInstallation).Clear the DTCs and test for normal operation.



Now, there are a few things I've noticed in monitoring:
1. Intake air temperature sensor is reading 55 degrees centigrade. Is this normal? Shouldn't it be the temperature of ambient air? Or is the air heated pre-combustion?
2. MAF sensor 2 seems to go wildly out of kilter with sensor 1. My assumption is that both should read roughly equal and within about 10% of each other at all times? Sensor 2 goes hundreds of kilos per hour more than sensor 1


So, the net is now narrowing to EGRs, a few sensors or potentially the right turbo. I've checked and tracked the turbos before and no issues with commanded vs actuals and same again today (albeit I didn't follow the instructions above, I did close enough to check it was operating correctly).

Thoughts? 2015 Range Rover Autobiography 4.4 SDV8

Morning Gary, first thing to check is the 2x 'L' shaped inlet hoses on top and to the front of the engine. They often split with age and will give the symptoms you describe. Once you have intake air either entering or escaping upstream of the MAF sensor it sends the system haywire. Could of course be something altogether different, but it'll take you two minutes to check these for splits and if you're lucky, you find one and you've got yourself a cheap and easy fix.

Unfortunately, it's not the hoses. They're fairly new with no splits. 2015 Range Rover Autobiography 4.4 SDV8

Ok, well at least you can eliminate those then. Could still be an air leak though. If you have access to a combustible aerosol (Brake cleaner is ideal), spray it all around the intake system with the engine idling. If the revs pick up you've got an air leak somewhere.

My money is on a hairline crack in the Inlet Manifold. Well known fault, especially on the 3.0L engine in the Jags etc. You will need a HIGH Pressure test to find it.

Do you mean the air inlet manifold or a rocker cover? 2015 Range Rover Autobiography 4.4 SDV8

The inlet system. Hose connectors, inlet manifold connections, where the inlet connects to the heads, etc etc. Don't rev it though, only do it at idle so the turbos are not boosting. The reason being is that at idle if there is an air leak it'll suck in the 'combustible', but if you spool up the turbos they'll pressurise the intakes and blow any combustible away (From the area of the leak, if there even is one).

Air inlet Manifold. Although just seen your readings for MAPT are normal so maybe not? I have heard of EGR gates sticking. just a thought.
The inlet manifolds (which are only plastic!) give way due to an excess of flexing from both turbos putting out so much pressure. They have since upgraded to a thicker one I believe.

I think I've found the cause. A big 1.5" gash in an intercooler pipe. I've quickly bodged it with gaffa tape and seems largely sorted.

So, I'll replace the pipe then see if issue resolved.

I've picked up a pair of EGRs with coolers and my thermostat housing needs doing so, I'm tempted to just replace them at the same time. 2015 Range Rover Autobiography 4.4 SDV8

That'll do it. Drive it very gently until you get it sorted as only a small amount of turbo boost will blow a hole in that tape. Basically what you're now getting is un-metered air into the engine.
What happened is the MAP (Mass Air Pressure) sensor records how much air passes over it, and for a given amount of engine revs, throttle position, engine load the control module will provide the correct amount of fuel for that given amount of air. As soon as there's a hole in the intake tract it's either sucking in, or under boost, blowing out air upstream of the MAP sensor.
What happens then is the control module continues to inject what it thinks is the correct amount of fuel based on the info the MAP sensor has provided, but because the actual air quantity is different it messes up the fuel burn which is then picked up by the O2 sensors in the exhaust.
What you then get is an implausible signal that throws up all manner of 'faults' suggesting this that and the other component is the problem, when in fact the cause is nothing more than (in your case), a split hose.

New intercooler hoses ordered, which will hopefully arrive tomorrow.

No soot since the gaffa tape bodge.

Here's the split.

Click image to enlarge

Intercooler hoses replaced and now nice and clean at cruise or a normal acceleration however, still heavy clouds of black soot under heavy acceleration.

How do I tell the difference between the whistle of the turbos and an air intake problem?

Could the fault be an EGR with an issue, it's just not sticking up a fault? 2015 Range Rover Autobiography 4.4 SDV8

Good news. You'll find the soot calms down after a while. The PCM (Power Control Module) has been trying to compensate for the mixture all being cocked up, and will gradually re-learn the correct values.
As for the whistle, anything more than a fairly quiet but obvious whistle at high engine loads (When the turbos are boosting hard) is more likely to be something like knackered turbo bearings. A split intercooler makes a really obvious howling noise.