Gurus of the diesel, I summon thee! (Audi TDI issue)

Help!

I have an Audi A6 -08 3.0 TDI Quattro Wagon (Manual). A lovely PanzerWagon with an entertaining drivetrain – or so it used to be...

I have a super weird issue: The car is drastically down on power. It feels as if I’m running with zero boost and the car is brutally tired. I have no CEL, no flashing coil light, nothing at all that my OBD2-scanner can find. It starts easily and runs without stumbling or missing, bit it has nooooo power and I can’t figure out what’s wrong.

• I have checked that the turbo actuator is moving freely and that it moves (checks range) when the ignition is turned on.
• I have double checked the air filter and ducting – all good.
• Turbo has a bit of old oil spill around it, but there is pretty much no play in it and the car doesn’t smoke. No weird noises.
• I have checked the piping turbo – intercoolers – intake superficially from the top and found nothing wrong.

Stumbling on the dark on this one, I have made the following ToDo:

• Swap diesel filter and fill the new filter with injector cleaner. I don’t expect this to solve the issue really, but I have run the fuel tank to almost empty twice recently and the fuel filter is right up top, so I’ll go ahead and do it for peace of mind.
• Lift the car, remove the belly pan and better check for boost leaks.
• Give up and take it to the dealership to have it hooked up to some serious diagnostic equipment.

Any advice or guidance would be appreciated. We have plenty of snow here and I SHOULD be drifting this beast daily… 

Pull the DPF off and have it steam cleaned or replace it.

In reply to JesseWolfe :

That is a good one! I have been doing a lot of short trips lately, which I understand is a killer for the DPF. 

Clogged exhaust, in other words - I didn't think about that. Many thanks!

Normally dpf clogs will throw a light.

I would suspect an injection pump is giving up the ghost.

Check dpf and cat.

Check all the emissions stuff. We have a cayenne diesel with the same motor, when it starts getting super laggy, it's all coked up.  EGR clean up/replacement, EGT replacement, cat replacement, etc, etc

In reply to Ranger50 :

Do modern diesels still white smoke when the injection pump is going?  Or have they been refined enough to not show smoke?

Worth checking the lift pump (or whatever it uses for one) and filters before changing the injection pump though.

docwyte said:

Check all the emissions stuff. We have a cayenne diesel with the same motor, when it starts getting super laggy, it's all coked up.  EGR clean up/replacement, EGT replacement, cat replacement, etc, etc

Excellent, just what I wanted to hear!   Buuhuhu! 

Mr_Asa: Currently, the car doesn't smoke at all. I'll absolutely go thru the filters before I swap the pump.

I find it weird that the car is not throwing any codes. I must say, I've never been driving along and begging a car to light up the CEL before! Some kind of failure code would narrow down the search a lot. A clogged DPF should generate a warning light, as should any failure of electric components. Not sure about the high-pressure fuel pump... I'll keep you posted. 

Update! Weird stuff is happening!

As planned, I went ahead and replaced the fuel filter, since it is placed right up top in the engine bay and since I've driven the car to an almost empty tank twice lately. I didn't expect it to actually do much. I also poured 3 bottles of injector cleaner into the new filter (it's a biiig filter). 

Well, something happened! It's not restored to former glory, but it drastically reduced the problem. The car has a lot more power, but it is not fully cured. Can it be that two separate issues has been pestering the poor German? 

The car runs much better under 3000rpm now, but quickly falls on its face at 3200 - supporting the theory of a clogged PDF. Still no codes, CEL or similar. 

I'm very tempted to disconnect the fuel filter again tomorrow and fill it with a few bottles of DPF cleaner magic stuff whateveritiscalled. But... the adult thing would be to pay to have it hooked up and diagnosed. 

We had a 2006 Audi 2.0l TDI.  It started, idled, but had exactly zero acceleration one morning.  We changed the EGR valve and it was as good as new.

The DPF on our Saab 1.9TiD, when it's full, doesn't seem to have any effect on our power/acceleration.  We just get a notification that it's full, so I go blast down some B-roads for a bit.  (Rinse, repeat as necessary).  It's worth noting that the EGR on that one sticks itself "open" bi-monthly though.  Probably because I insist on cleaning it instead of changing it.  The symptoms for that are laggy acceleration (ie:  I stab the gas.  the car thinks about it for a bit, and THEN we go!), and hard starting when it gets REALLY bad (stuck wide open).  No lights/warnings with that one.  Just butt dyno results.

I didn't know a Panzer Wagon with such engine/trans combo existed.

I think that did it! I took the car to work this morning and it appears to be all there. It pulls as strong as ever and happily (for a diesel) revs to red. Ooooh those 3rd gear pulls are entertaining, I tell you...  

So the fuel filter was clogged, no doubt. Not sure what made the difference from yesterday evening and today. Maybe the injector cleaner did its magic overnight or perhaps the ECU decided to get rid of some limp-home codes or... whatever. But as for right now, after my 20min drive to work, the car is all good. 

I've added some DPF cleaner to the tank (and I'll make that a habit too) and we'll be using it for a longer trip this weekend. Crossing my fingers it was as simple as a fuel filter!

dxman92: I'm in Sweden. Perhaps this spec was available on the EU-market only? 

Now that everything seems to be functioning...

When I was a service writer I'd always have to tell the old ladies that just drove their cars to the grocery stores and back home something, based on what you said your usage is I think it will help you as well.

Once a week, just get on the highway.  Get it up to the max speed limit for a solid 20 minutes at a minimum.   Let everything work as it is supposed to

In reply to Mr_Asa :

Way ahead of you...

I was a turbo engineer for Cummins for a few years.  The trucks that were babied had tons of issues with the dpf and turbo canes sticking. The trucks that didn't were worked hard every day.  Stick it in third and do a redline pull merging on the highway once in a while and you'll be fine. 

In reply to Fueled by Caffeine :

Once going to work and once going home, every working day!   Trust me, I didn't buy this car to fart around in it.