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egr valve is forming soot stones


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Hello all,
I am new here, Because my sisters car a toyota Auris 2.0D from 2007 with ade-150 (1ad-ftv) engine and particulate filter shows strange symptoms,
at first the egr valve clogged every 3 months resulting in p0400 code, after cleaning the egr valve everything was okay again (have done this for about a year).
But now my sister was in a breakdown and had called the toyota garage and towed her car to the toyota garage. after putting in a new egr valve, the car broke down after 2 days and the garage towed the car back and was in the toyota garage for a week, then the car drove well for 3 weeks and then the p0400 code came back ,
this time i cleaned the valve, but now this new egr valve gives the code every month with (here comes the weird symtom) soot rock formation that the valve stays open with a soot stone in between, after valve removal, and after discarding from the small stones, i delete the code and after a month he has it back. Has anyone here heard of soot stones?
What I have already checked and measured,
mass airflow sensor with iat sensor cleaned. iat sensor measured and resistance is 2.6k with 22 degrees C (72F),
checked with scan tool throttle body sensor to map sensor and everything moves together on the graph with to the throttle pedal posistion.
Thanks in advance, Mosco
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P0400 = Exhaust Gas Recirculation Flow and the EGR valve could be a potential cause however the fault is not specific to the valve what the car is seeing is a lack of change when instructing the EGR valve open " Mass air flow rate is not changed when turning on the electric EGR control valve while decelerating.(2 trip detection logic)" Areas of potential issue are:


  1. EGR valve deposit
  2. EGR valve passage deposit
  3. Air intake system (leaks or blockages)
  4. Exhaust gas leaks
  5. ECM
  6. Mass air flow meter
  7. Manifold absolute pressure sensor


If as you say one of the EGR valves is new then it is unlikely this is the fault however there is way more to the EGR circuit than one valve, see:


on this engine Exhaust gas exits the exhaust manifold into the EGR cooler ( known to block and restrict gas flow ) see green line, after the cooler gas passes through the primary EGR valve see blue line, from here it passes through the cylinder head see purple line then finally through the secondary EGR ( likely the one you have had replaced) see red line

Depending on setup you may not have the primary EGR after the blue line, it has been seen before for lump of carbon to break away from the EGR cooler even more so if the cooler is leaking coolant into the EGR flow are you loosing any coolant? 

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thanks for responding and trying to help,

the car has no big oil consumption and the coolant loss is maybe 3ml in 6 months, almost nothing.Before the new egr valve, the car never had this symptom, And with the old egr valve (I think it was never broken) the soot build up in the inlet was minimal, I just had to remove a little soot and it ran again. My first thought was that the inlet collector was clogged, but now after that new valve he has this problem,little soot stones. I also put forte diesel injector and forte turbo cleaner in it, but it didn't do anything, I also put in new oil and a new diesel filter with air filter. idle is very stable just those little rotten soot stones, i called 5 different toyota garages and no one has heard of this problem, so i thought i'd check this forum.

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i would be looking at the EGR cooler and give that a proper clean most diesel 2005 onward do not respond well to short runs they just soot up in no time

Edit. When was the fuel filter last changed or drained ??

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about 2 months ago I replaced the fuel filter before I added the forte additives,

the egr cooler is at the back of the engine, can you remove it like that?

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got more information,

car coolant has not yet been replaced (long life pink and still look nice pink) and the original glow plugs are also still in it,

the car has 165000 Km, but starts without problems and always has a stable coolant temperature (always in the middle), have tested the coolant with dmm to see if it is still good, 0.112V (I don't know if this is a reliable test ). and coolant temp with scan tool is 86°C.

these were also the conditions before the rocks formed in the valve. and in 1 week without driving and installing a new valve, would a cooler just get clogged like that? is there any way to find out if you have a clogged egr cooler without taking it off?  

also doesn't have an exhaust leak,


is it a big job to take the cooler off?

is this engine not in other toyota models such as avensis, verso, Rav4, corolla, etc. and no one else has experienced anything like this before, strange








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No, threw them away

it looks like Black basalt gravel like for a driveway with sharp edges. but only light gray in color and soot.

usually they are small and then there is one clamp between the valve, the largest was about 7mm.

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  • 3 weeks later...

problem is back after 3 weeks and I have now taken pictures of the blocked valve in fixed position with the stones, now they are a bit darker than normal. The only difference is that I cleaned the air mass meter again.






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Good grief, I wonder how those formed?!

My old Yaris D4D's EGR just had powder soot baked all inside it but it was quite an even coating and didn't form lumps like that!


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Without fault the soot would normally slowly coat the walls of the EGR system, to form chunks like this it needs something to bind the soot:

oil would make a sticky wet soot and also potentially show as oil loss and blue smoke on startup or under load

fuel would be similar only slightly less wet and sticky this would also likely show as oily smelly white smoke on startup or under load 

which leaves water/ coolant a leak in the cooler even small would form a wet spot which will bind more and more soot until it builds up and forms a small restriction which then breaks off and runs through the egr system until it hits the valve such a small leak may not show as significant coolant loss or even create any steam/smoke

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