Car failed smoke opacity test but no fault codes. 

The smoke is black and only visible if looking closely at the exhaust outlet.   It only appears on rapid rpm increase, not at steady high rpm.

The car seems thirsty, best I can get out of it is 40mpg.

I've been offered a variety of expensive options to potentially solve it but none based on any sort of firm diagnostic testing.

I'm amazed that nobody in the trade seems to be very interested in taking a logical approach to finding the best starting point!

My thinking is that if there are no fault codes something is going wrong which the system doesn't recognise.

I plan to start by checking the differential pressure across the DPF to see whether the sensor has failed in a position that will not induce a DPF regeneration.  A decent diagnostic device should be able to show a plot of rpm/pressure.   If the pressure is high it suggests a blocked DPF.  If the pressure reading doesn't change it suggests sensor failure.

I need to take the car somewhere to get that done.

If the sensor is functioning normally I will start dismantling, starting with the EGR valve, if that is working I will take out the  injectors and get them tested. 

If all of that is operating correctly then I guess the DPF filter is probably the issue. 

Have I missed anything obvious before I set about on trying to sort this out?

You can use Forscan to check the DPF pressure differential yourself.

Soot particles shouldn't be able to pass through the DPF core.  So if there is black smoke, the DPF core may be cracked or not sealed to the can properly.

Also worth giving it a good hard blast, as very small particles can build up on the inside of the exhaust if the engine isn't revved hard.  (Guessing a Grand Tourneo doesn't do many traffic light Grand Prix's).  The MOT garage should always 'purge' the exhaust before the test to blow these out but some are cautious of engine damage or pushing an old cambelt too hard.

And the Test should have been done on a hot Engine, i.e. soon after the car had been driven to the Centre fully warmed up, not when the car was cold and sat at Idle to get the temperature up.

1 hour ago, Tizer said:

And the Test should have been done on a hot Engine, i.e. soon after the car had been driven to the Centre fully warmed up, not when the car was cold and sat at Idle to get the temperature up.

It was done with the engine hot, they revved it to nearly 5,000 which I thought was a bit harsh.

3 hours ago, TomsFocus said:

You can use Forscan to check the DPF pressure differential yourself.

Soot particles shouldn't be able to pass through the DPF core.  So if there is black smoke, the DPF core may be cracked or not sealed to the can properly.

Also worth giving it a good hard blast, as very small particles can build up on the inside of the exhaust if the engine isn't revved hard.  (Guessing a Grand Tourneo doesn't do many traffic light Grand Prix's).  The MOT garage should always 'purge' the exhaust before the test to blow these out but some are cautious of engine damage or pushing an old cambelt too hard.

It had a good blast with the basic redex diesel treatment before the test.  I have since put a bottle of Wynns pre mot additive in it and given it a good bit of stick.  I can still see a small puff of black smoke if I put my foot down hard so guess it would fail again.  Not sure about forscan, will look into that. 

11 hours ago, Grand Tourneo said:

It was done with the engine hot, they revved it to nearly 5,000 which I thought was a bit harsh.

That is the way to purge it.  The purge isn't so much about heat as airflow.  It needs maximum airflow to blow anything out that was otherwise left stuck on the walls of the exhaust pipes and boxes.

I've never found fuel tank additives to make any difference personally, and wouldn't generally recommend them, though some people claim good results.

Since 2018, any visible smoke from the tailpipe of a DPF equipped vehicle is now an MOT fail, so it does sound like it would still fail for that.

 

As it seems that it was purged and has been given a 'damn good thrashing' then it sounds like your smoke issue is ongoing rather than just previous build up.  DPF differential pressure is definitely the next thing to check now.

2 hours ago, TomsFocus said:

That is the way to purge it.  The purge isn't so much about heat as airflow.  It needs maximum airflow to blow anything out that was otherwise left stuck on the walls of the exhaust pipes and boxes.

I've never found fuel tank additives to make any difference personally, and wouldn't generally recommend them, though some people claim good results.

Since 2018, any visible smoke from the tailpipe of a DPF equipped vehicle is now an MOT fail, so it does sound like it would still fail for that.

 

As it seems that it was purged and has been given a 'damn good thrashing' then it sounds like your smoke issue is ongoing rather than just previous build up.  DPF differential pressure is definitely the next thing to check now.

Forscan interface ordered so I'm now looking for a laptop with windows to run it on.  Hopefully it will show a lot more than a basic OBD code reader.

I was surprised at how accessible the egr valve is once the wipers are off and the front apron trays off.

 

EGR had a light covering of dry soot with no sign of oil, which I've seen on other cars.  Good clean and going back on now ready for injectors to come out and go for testing.

Quite impressed with how easy it was to get the injectors out.  Need to get them tested now.

They look a bit wet and mucky on the tips, not sure if they should look like that?

Looks like the copper washer might have been leaking on the right hand one at least.  Not a major issue but it does reduce the compression so you don't get such a clean burn.

I wouldn't expect to see that much diesel on the tips either tbh, unless it's run-off from penetrating fluid used before removal?

1 hour ago, TomsFocus said:

Looks like the copper washer might have been leaking on the right hand one at least.  Not a major issue but it does reduce the compression so you don't get such a clean burn.

I wouldn't expect to see that much diesel on the tips either tbh, unless it's run-off from penetrating fluid used before removal?

No penetrating fluid needed to get any of these out, they were a doddle!  The stuff on the tips is as they came out, diesel has leaked out of one of them since so that doesn't seem right.  It looks like they are all damp above the seal level, although not burned on like some I've seen.  I guess for a car on 102,000 that isn't massive leakage.

When I put the cleaned out EGR valve back on and gave it a bit of a boot there was a big cloud of soot/smoke from the exhaust so don't know what that was all about.

I've ordered some cleaner to put in the DPF to see if that helps, it doesn't look as though the DPF should be too tricky to get off if I need to change it.

Hopefully some of what I'm doing will improve fuel economy a bit!

Not surprised they came out easily if they were all lubricated with diesel.  

The engine may have been switched off mid DPF regen.  During regen there is a lot of excess diesel in the cylinders.  The idea is that diesel is injected after TDC, so doesn't burn in the cylinder but gets blown down the exhaust instead, it then ignites when it hits the hot cat and burns the soot in the DPF.

The injectors on these are the main weak point, so I wouldn't be surprised if one or more needs replacing.  I would also recommend re-cutting the injector seats before refitting with new copper washers.

46 minutes ago, TomsFocus said:

Not surprised they came out easily if they were all lubricated with diesel.  

The engine may have been switched off mid DPF regen.  During regen there is a lot of excess diesel in the cylinders.  The idea is that diesel is injected after TDC, so doesn't burn in the cylinder but gets blown down the exhaust instead, it then ignites when it hits the hot cat and burns the soot in the DPF.

The injectors on these are the main weak point, so I wouldn't be surprised if one or more needs replacing.  I would also recommend re-cutting the injector seats before refitting with new copper washers.

Took the injectors into AGNG in Bicester this morning, they very helpfully did a quick electrical check on the old injectors and advised that they were all on the way out.  Didn't fleece me for a full test, which would have been a waste of time.  Bought a new set for a very reasonable price so now got to fit and calibrate them.  A neighbour is digging out an old laptop so that I can download For Scan, which should allow me to do that and check other things.

Just checked the injector seats and they are all very clean, expected to find the copper sealing washer in No. 3 cylinder but it wasn't there so that cant have been helping things!

This engine doesn't have a differential transducer across the DPF, it just measures the upstream pressure, which makes sense.  I can check that reading also once the ForScan thing is up and running.

It will be interesting to see if the fuel economy improves!

2 hours ago, Grand Tourneo said:

This engine doesn't have a differential transducer across the DPF, it just measures the upstream pressure, which makes sense.  I can check that reading also once the ForScan thing is up and running.

I stand corrected on that.   Very odd as the same 8v engine in the Focus used a differential sensor.  If you do end up buying another DPF, will have to check carefully to make sure it only has the one pressure pipe.

Forscan downloaded and injectors coded,  car runs fine but still got the smoke on hard acceleration 🙄

Going to have a look at the DPF pressure tomorrow the see if a regen helps.

Forscan is an interesting tool!  I set it up again today and did some live data viewing on DPF soot levels and pressure. 

Soot levels 25%  (Apparently soot levels can go way over 100% and on most cars regen isn't triggered until 100%)

Upstream DPF pressure 0.4kPa at idle rising to around 9kPa at 3,000rpm.

No suggestion of blockage there but that doesn't prove that the DPF isn't damaged internally.

When I drive the car with the live mpg showing on the dashboard the mpg does seem to dip very low on acceleration so I'm wondering if, even with the new injectors fitted, it is over fuelling at that point.  Once cruising speed is reached the mpg increases significantly.  I realise that is to be expected as the loading reduces but it does seem thirsty on even moderate acceleration.

Going to have a look at the O2 sensor outputs next to see if they may be having an effect. 

Can't seem to find an O2 sensor voltage check on forscan, there must be a sensor somewhere surely?

The car is now worse with an average fuel consumption figure of 38.5mpg 🤨

At a loss to what to try next, it really is pain!

1 hour ago, Grand Tourneo said:

Can't seem to find an O2 sensor voltage check on forscan, there must be a sensor somewhere surely?

FORScan may not monitor the O2 Sensor if your Engine has one.

My Mk2.5 TDCI did have one but there was nothing in FORScan for it and anyway because Diesel Engines work on an excess of Oxygen all the time, I have yet to see anything definitive about what readings are expected.

I'm also sure that the Sensor on my car was a Wideband one, so they do not work the same way as the older type and there is no Voltage to be monitored, the Sensor tries to keep the Current to 0 in a Petrol car but that is not applicable to Diesel.

If you have any definitive details of what to expect when monitoring a O2 sensor in a Diesel then I would be interested in seeing it.

Edit @Grand Tourneo, remembering back, although I could not monitor the Sensor in FORScan there once was a Fault Code for it, I don't think it did light up the MIL Light and because the car was driving as before I Ignored it and the next time I checked the fault was not there, which is a long way of saying that if your Sensor was faulty then it is highly likely that a Fault Code would show up.

From what I've been reading a failed O2 sensor that gives a low voltage can trigger the engine to add more fuel to richen the mixture.  That could be totally wrong of course.

I'd like to get someone with a proper full on diagnostic device to check and see what is actually going on. 

It is definitely using a lot of fuel, I've set up the new injector codes but that doesn't seem to make any difference. 

These Sensors are monitored to within an inch of their lives in Petrol cars, I'm not sure about Diesel ones, and if it is a Wideband one they do not produce a Voltage, they are fed with a variable Current.

Thinking about it logically, it is most likely a Wideband one. Usually Wideband ones have 6 wires, Narrowband ones only 4 wires.

I don't know what you have been reading but was it for Diesel Engines, if not then I would say it is not applicable.

The O2 sensor on modern diesels is only used for EGR control.  (And Adblue, where fitted).  It's not used for fuelling like it is on a petrol. 

NOx is created during lean running when there's excess oxygen in the cylinders.  Exhaust gas is mostly made up of inert Nitrogen.  Opening the EGR partially fills the cylinders with that Nitrogen first, which physically prevents more oxygen entering the cylinder from the air outside.  Less oxygen in the cylinders means less NOx from the tailpipe.

Forscan is almost a direct copy of the Ford dealership diags.  There isn't a better device.

The new injectors will need a few miles to bed in.  How many miles have you done on them?

I take it there are no fault codes on the PCM at all?

Given how sticky the injector tips were, I'm wondering if the turbo vanes are gummed up.  I take it it is a 115ps model with VNT?

2 hours ago, TomsFocus said:

The new injectors will need a few miles to bed in.  How many miles have you done on them?

I take it there are no fault codes on the PCM at all?

Given how sticky the injector tips were, I'm wondering if the turbo vanes are gummed up.  I take it it is a 115ps model with VNT?

This is the 85kw 1.6tdci  I'm no expert on Ford variants and to be honest have never really liked them.  This vehicle just happened to have the biggest practical load space in an estate car version. 

The EGR valve had no oily deposits, just dry soot which easily washed off, not sure whether the fuel additive I used helped to free off some of the muck that was sticking to the injector tips. 

Not sure how long the injectors need to bed in? I've done about 50 miles since fitting them.  I've set the codes on the individual injectors using the forscan but it only allowed me to enter the first 6 characters of a much longer string on the injector. 

The original injectors had the same string length and the characters were correct to the original settings when checked on forscan. 

No faults at all showing on forscan.

I'm at a loss to understand what else can be causing the problem at this point.

Maybe I need to try and find someone locally who can do the setup and check that it all looks OK. 

10 hours ago, Grand Tourneo said:

This is the 85kw 1.6tdci  I'm no expert on Ford variants and to be honest have never really liked them.  This vehicle just happened to have the biggest practical load space in an estate car version. 

The EGR valve had no oily deposits, just dry soot which easily washed off, not sure whether the fuel additive I used helped to free off some of the muck that was sticking to the injector tips. 

Not sure how long the injectors need to bed in? I've done about 50 miles since fitting them.  I've set the codes on the individual injectors using the forscan but it only allowed me to enter the first 6 characters of a much longer string on the injector. 

The original injectors had the same string length and the characters were correct to the original settings when checked on forscan. 

No faults at all showing on forscan.

I'm at a loss to understand what else can be causing the problem at this point.

Maybe I need to try and find someone locally who can do the setup and check that it all looks OK. 

85kW is 115ps so yes it'll be VNT.  Some lower powered versions use a wastegate turbo instead.

On a side note, other members scoffed when I suggested this engine in a Mondeo based on my Focus experience with it...  It can't be all that bad if you're powering a whole aircraft carrier with it.

50 miles should be enough to bed injectors in, though I'd generally recommend around 100 miles to be on the safe side.

If it's not over-fuelling, then it could be under-boosting, though that should trigger a fault code.  You could watch MAF & MAP live readings to see if they are smooth or if there are any anomalies in the MAP figures as the engine load increases.  That could indicate a small boost leak that is only opening up under the initial boost surge.  The PCM will allow a few seconds of underboost before triggering the fault code, but that could be the cause of your single exhaust puff.

I will also say that 9kPa on a DPF suggests a fairly considerable ash build-up, assuming it was done after a regen.  That is about right for 10 years of ash, but definitely not clean/new.  I'm not sure how much ash build-up the PCM allows at this age.  However, again, I'd expect to see a fault code for it.

The biggest problem for me is not knowing what the normal values should be for the various parameters that forscan can check. 

I wouldn't mind betting that most "technicians" would be stumped if faced with an engine problem that isn't throwing fault codes.   

Need to find someone who has a lot of experience and is familiar with the things that are likeliest to be marginal.

Take your point about under boosting but again it is difficult to know what the normal values should be. 

I'm not sure about the dpf pressure having watched a few videos of them being cleaned.  They seem to start at way more than I'm seeing but again where do I find a list of normal values?

Not sure if the egr valve is working as it should, it moves as the throttle opens but where should it actually be?

Bit of a minefield really.

What boost pressure should I be looking for?

There isn't a list of normal DPF values as far as I'm aware, at least not available to the public.  It's just something that comes with years of experience seeing the stats on different ones.  A new DPF should only be around 2-3kPa under load.  I'd expect to be cleaning or replacing at around 12-15kPa under load.

There are different types of DPF cleaning.  Some are only breaking down compacted soot to be burnt during regen, in which case, the 'after' pressure won't be as low as a new DPF as it'll still have the same amount of ash inside.  The only way to clear the ash of out of a DPF is to remove it from the car and backflush it out the way it came in.

Too many variables with boost pressure.  You should be able to get it up to around 30psi on this engine under load. But the more important test is to check that the MAP pressure is following the MAF flow at pretty much the same rate on the graph.  If there are big differences between them, that suggests a fault with one of the sensors or the boost pipework.

Again, too many variables with the EGR.  It's used much more on the Euro 5 models than it was on Euro 4.  Generally it should be open to some degree during low load running and cruising.  And should close under heavy load.

I completely agree that most garage techs won't be able to diagnose this without any fault codes sadly.  If you can find a garage that can do it, they won't be cheap.  You'll generally find remapping type garages are better at this type of thing.  I don't mean the ones flashing other peoples maps, needs to be one with a rolling road that tweak the maps themselves.