2007 BMN Diagnosis thoughts Boost, Intake or EGR?

[BenTspanner]

So,

I recently got a P0401 Exhaust Gas Recirculation (EGR) System: Insufficient Flow Detected.

Stripped and cleaned the EGR but mil light returned on test drive. When I cleared the fault when warm, mil light did not return during several hours of driving until cold start. Then back on.

Cleared the fault again. Did not return

When on the test drive I was on the motorway during heavy rain with cruise control in and hit a patch of standing water which caused the ESP to kick in, cut out the cruise control and drop revs - it did it's job.

Immediately after, MIL light came on and car went into limp mode.

Limp worked for a while - going up hill with some weight in the boot - but then slowly died off, started to cough a bit and finally stalled out on an ext ramp up hill. During this time the DPF load coefficient started to climb quite quickly (ie pressure differential over the DPF) and was up to 54% by the time it stalled out.

The engine would then not restart.

Fault code P0299 - Boost Pressure Regulation: Control Range Not Reached was now logged on VCDS.

So far all I have been able to do is use a vacuum pump to check the turbo vane actuator which appears to be moving freely.

Anybody got any thoughts as to what may have caused the death here? Any ideas on further diagnosis with an engine that will not start?

Thanks in advance
Ben

 

[BenTspanner]

Sorry for clarity the car is a 2007 Audi A3 8P 2.0 TDI 170PD BMN engine with DSG gearbox

 

[aqibi2000]

What is the history of the car in terms of DPF regens and has the turbo been replaced or tinkered with?

 

[BenTspanner]

I replaced the DPF about 20,000 miles ago with a pattern part and brand new pressure lines and switch. it has been working seamlessly since. The turbo I replaced around 90,000 miles ago, again, perfect operation for all those miles. I do around 800 miles a week in the car but all motorway cruise control stuff.

 

[NHN]

90k is plenty for vanes to clog again tbh, given the boost error is exactly for when vanes stick, I'd remove & check this as going uphill is one way to test this.

 

[BenTspanner]

Update,

During investigation I found the valve head had fallen off the EGR valve shaft which caused the cough and stall and subsequent failure to start.

Great, so I replaced the whole EGR valve, started up first time. I did a long drive today, full array of driving conditions, windy roads, lots of motorway, heavy traffic and city. Everything was going fine, all parameters on VCDS in normal ranges.

Then after about 6 hours (with a few longish stops) I was on my way home at a fast motorway cruise for about 80 straight miles, when I came off the motorway and onto the back roads home - flashing glow plug lamp and vcds code “Boost control range not met”.

I cleared the code and got on home with no repeat.

I find it interesting that it happened at the same point near enough on the same motorway after the same length of drive.

Basically when you go back to normal driving conditions after a long stretch of fast motorway cruise - the last bit uphill with a bit of extra weight in the car.

I’m feeling like the turbo vanes sticking at their high boost position may well be the problem. Although the actuator moves well under vacuum test.

Thoughts?

 

[NHN]

I'd remove turbo & check, clean.

 

[BenTspanner]

Update,

I tried a can of Wynn's turbo cleaner on the intake side, did the same long drive and exactly the same set of symptoms. I logged it this time with VCDS for those who are interested, screen shots below. I have a 2-stage cleaning product coming to do the exhaust side this week - I'll report back after.

I also have yet to do a diagnostic check on the N75 but sticky vanes is looking like the culprit. I'm trying to avoid taking the turbo off until its actually to get it refurbed!

I'm interested if anyone who is more used to looking a boost traces will see the screen shots and have a more specific "well it's obviously this..." moment!

 

[NHN]

The cleaners are ****, only way to clean vanes is to strip the turbo & Dremel etc it back to the bare.

Waste of time using the cleaners as it's temp at best.

 

[aqibi2000]

Furthermore it would only start to improve when the exhaust side is cleaned