Thread: Leak in EGR system - how to seal?

Originally Posted by DiscoJeffster

Well given it’s a P006a I agree, but no amount of logging is going to say where the leak is.

OP, have you tried swapping the MAF sensors around? A change in failure behaviour might indicate a faulty MAF. I think this is really unlikely but if you can’t find a leak, which P006a implies, possibly worth a try

Hi,

yes I swapped the MAF sensors, to no effect.
Also swapped top intercooler hose this morning, to no effect.
One thing I noticed today that the bank 2 reading (primary) seems to not get above 180 g/s. Is that the point where the intake circuit 1 (secondary) should kick in?
because that is where a fault occured this morning. Shortly before i revved the engine and got a plausible reading from both MAFs with no fault. At the second try the MAF bank 2 peaked at 180g/s and the fault occured. Bank 1 MAF showed only 1.3 g/s or so.

Maybe this indicates a faulty solenoid, valve, actuator or whatever, so that the second air intake circuit doesnt open?
What valve exactly would be responsible for that? CSOV and/or TSOV?

Cheers,
Matt

Weirdly bank 2 is the primary MAF used at low load, with bank 1 the one that kicks in at 2500rpm ish, as I recall.

Clutching at straws i guess, but when one of the turboes failed in mine, i recall the air control valve was also swapped out. Seems to me that this may be the cause of your problems, the control valve doesnt work properly, boost can't be built up as expected based on load and engine rpm, sensor reads low map and throws a code.

This could all be wrong... So apologies if it is.

Have only just had a chance to take a look.

Of course nothing lines up with what I normally do tuning wise.. So had to start again.

I haven't got time to fully read the thread, and I have no idea how the 3.0 system works, but these are my observations.

^^read disclaimer!

MAF bank 2 seems to be always operational.

MAF bank 1 kicks in somewhere around 2500 RPM.

Both banks added together are roughly equivalent to total mass air flow...I don't know how much discrepancy is allowed.

IAT seems either incorrectly labelled or is reading abnormally low.

AAP has very little deviation which is also unusual, and if the manifold absolute pressure reading is indeed what it says...
I.e. absolute, something is wrong, it's reading lower than AAP.

In fact I'd say it's defaulting at lower pressures.

If everything is labelled correctly and is displayed at the correct factor, I'd say the map sensor is either faulty or the wrong one.

These are just calculations based on basic direct injection diesel theory, if there are any tricks going on behind the scenes this data will be wrong.

Just out of interest, does the gap tool display boost or calculated boost, it would be interesting to watch that number as you drive along.

What was your altitude and ambient temp when you did the log?

The log was interesting actually, took about an hour to convert everything, but I can now handle logs from the gap tool and make them legible!

Originally Posted by DiscoJeffster

Weirdly bank 2 is the primary MAF used at low load, with bank 1 the one that kicks in at 2500rpm ish, as I recall.

Yes, thats how I understood it as well. Sorry if my last post was a little confusing.

However, as I was getting faults way below 2000 rpms (while accelerating at relatively high speed uphill), I believe this could be more Load than solely rpm related.

I think we might be onto something here.

My theory: Maybe it is not an air leak, but a problem with opening the secondary air intake system. Because on my last post with the logs, the primary MAF peaks at 180g/s, so the car somehow calculates something and trys to activate the secondary air intake, which would then lower the primary MAF reading. As this does not happen (sticky valve / actuator maybe?) it goes into fault. You can see that I have no secondary MAF reading in the yesterday logs. And I could also observe this today, when, first both MAFs showed a reading and fault didnt occur and when trying again, only primary MAF shows flow and secondary MAF stays at very low flow.

Originally Posted by Eric SDV6SE

Clutching at straws i guess, but when one of the turboes failed in mine, i recall the air control valve was also swapped out. Seems to me that this may be the cause of your problems, the control valve doesnt work properly, boost can't be built up as expected based on load and engine rpm, sensor reads low map and throws a code.

Hi Eric,
thanks for the reply. What exactly do you refer to with air control valve? It would fit the symptoms, I guess…

Cheers,
Matt

Originally Posted by shack

This could all be wrong... So apologies if it is.

Have only just had a chance to take a look.

Of course nothing lines up with what I normally do tuning wise.. So had to start again.

I haven't got time to fully read the thread, and I have no idea how the 3.0 system works, but these are my observations.

^^read disclaimer!

MAF bank 2 seems to be always operational.

MAF bank 1 kicks in somewhere around 2500 RPM.

Both banks added together are roughly equivalent to total mass air flow...I don't know how much discrepancy is allowed.

IAT seems either incorrectly labelled or is reading abnormally low.

AAP has very little deviation which is also unusual, and if the manifold absolute pressure reading is indeed what it says...
I.e. absolute, something is wrong, it's reading lower than AAP.

In fact I'd say it's defaulting at lower pressures.

If everything is labelled correctly and is displayed at the correct factor, I'd say the map sensor is either faulty or the wrong one.

These are just calculations based on basic direct injection diesel theory, if there are any tricks going on behind the scenes this data will be wrong.

Just out of interest, does the gap tool display boost or calculated boost, it would be interesting to watch that number as you drive along.

What was your altitude and ambient temp when you did the log?

The log was interesting actually, took about an hour to convert everything, but I can now handle logs from the gap tool and make them legible!

Hi shack,

wow thanks for your thoughts! It is really appreciated!

Regarding the MAF 1 and 2 I believe youre totally right how the system works.

IAT seems correct. As I am based in Germany and we have about 2-4 degrees Celcius right now.

AAP also seems correct to me, as this should always be the constant pressure of roughly 100 kPa, or no?

MAP sensor was swapped, so I would guess its ok, but not guaranteed of course.

Out of curiosity: how did you convert the csv logs to make them readable?

I will try to check for boost related values and report back.
EDIT: Boost related live values are:
Boost pressure actuator - Bank 2 - Controller output
Boost pressure actuator - Bank 2 - Desired position
Boost pressure actuator - Bank 2 - Measured position
Commanded boost actuator control - Bank 2
Boost absolute pressure - Raw value

I logged these values together with engine rpms, map value and maf bank 1 (secondary). The first screenshot shows where I believe the fault was triggered. I was just accelerating, no manual shifts. And also there was an air flow in bank 1, basically disproving my theory that the opening of the second air intake was causing this.
IMG_7963.jpg (original: iCloud Photos - Apple iCloud)
for reference values a screenshot from afterwards:
IMG_7964.jpg (original: iCloud Photos - Apple iCloud)

@shack: csv is attached, maybe you can see something here. I dont know how to interprete them at the moment.

Cheers
Matt

Can you have the gap tool in normal driving mode and get a calculated boost number?

As mentioned before, I have no idea with these cars, but at idle manifold absolute pressure and ambient pressure should be roughly the same.

In the log I did yesterday, manifold absolute pressure was sitting at 76 kpa, this translates to roughly 2300 above MSL.

Germany may be that elevated, I don't know.

But the AAP sensor says 100kpa, so that's basically sea level.