2.5 TDI AKE Quattro Advant noise when warm - some performance loss help

LayerzA3

Registered User
Hi all, not posted much on here back when I had my A3 but now as a 2.5 tdi owner I can see there is lots of knowledge on here about 2.5 TDI's and I seem to have an issue that as far as I can see does not fall under previous threads I've read - some very very long!

I will outline the issue and then the things I have done so far - later today I will try to get a video of the noise.

So the issue is that once warmed up thre is a plinking or almost air sounding noise (sounds like chtuk chtuk chtuk) that increases with RPM.
When you first start the car (is starts first turn every time) it's much smoother until warmed up when you start to notice this noise.

I will now explain the second issue which may or may not be related, when the car is colder (so not yet at 90 on the temp gauge which it does get to much quicker then my old 1.9) if you need to give it some hard acceleration and change gears and step on it again it will chug and stumble until you depress the clutch let the revs drop and go again and it's fine.
Once warm this issue goes away - this issue again could be unrelated and this weekend I wan't to Mr Muscle the turbo in case it's coked up on the VNT rings.

The last factor - again maybe this is VNT ring or perhaps the noise itself, occasionally I put my foot down and the car feels amazing perhaps upwards of 20-30hp of what I usually see.

Now for things that have been done and not resolved things:
Injectors reseated with new washers
Fuel filter and union changed
Injector return lines replaced
VCDS code's all checked fine
CAM's are fine - when I changed the injector seals they looked great.

Car is on 189k miles atm - I understand the IP was rebuild by DieselBob at 100k not sure if any rebuilds after this point.

I have a few things I'd like to still check but one of which I think I need full VAGCOM for timing checks?

However at this point just seeing what thoughts and opinion's people have, things I could be checking I might be missing or overlooked.
 

pauldazzle

Registered User
My first suspect with any temp related issues on VAG cars is the coolant temp sensor. Very common failure & often doesn't throw a fault code.
N.B. CTS has 2 independant outputs, 1 to the temp guage & the other to the ECU.
If you have VCDS go into engine measuring blocks & see what temp the reading the ECU is getting from the CTS.
 

LayerzA3

Registered User
I've run some logs and will check later but pretty sure the dash and vagcom were pretty close, as in once warm dash shows 90 and light running VCDS showed 89 and after some hard pulls moved to 91.

It does make me wonder if it's worth picking 1 or 2 up to see what happens.

Out of interest would the line of thinking here being bad temp sensors retarding or advancing timing?
 

abyrne153

Registered User
You can check the operation of the VNT by removing the 2 x 10mm studs holding the actuator mechanism the the turbo body. Once removed the arm should move freely without any stiffness. If it doesn't then the VNT mechanism likely gummed up. Check also your EGR valve. This can also jam causing a performance issue and doesn't throw a fault code on the A series engine. It can be blanked off without causing the EML to come on.
 

LayerzA3

Registered User
You can check the operation of the VNT by removing the 2 x 10mm studs holding the actuator mechanism the the turbo body. Once removed the arm should move freely without any stiffness. If it doesn't then the VNT mechanism likely gummed up. Check also your EGR valve. This can also jam causing a performance issue and doesn't throw a fault code on the A series engine. It can be blanked off without causing the EML to come on.

Thanks I didn't realise the VNT's on these were held on in that way, though being honest I haven't looked at the turbo too much. I know it moves straight away on start up and when measured in VAGCOM there is some lag in it's response to duty cycle requests - can check movement this weekend hopefully paired with a Mr Muscle clean.

Things I forgot to mention - I'm running a hybrid turbo and no EGR but I've not felt the turbo was at fault for the noise issue and it makes boost requested of it.
 

pauldazzle

Registered User
If temps look ok in VCDS then your CTS is fine.
 

LayerzA3

Registered User
If temps look ok in VCDS then your CTS is fine.
See I'm mostly thinking that but wondering if when cold the connection is bad...or it's had better days and maybe is a bit tempermental.
My thinking here is oddly linked to 3D printing where I have nightmares with thermistors

There have been a few times I've been out with VAGCOM and my camera from cold and the car decides to behave.
 

LayerzA3

Registered User
OK Video uploaded - first bit when it's damp is cold then cut to when warmed up.
Second bit when lighter is leaving work when cold and pulling onto motorway after sitting in 3-5 mins of traffic.

(unsure how to edit this into first post)
 

LayerzA3

Registered User
Bumping a bit as video attached of Engine noise above

Also took it out today and it was up to 90 very quick within 4 minutes - I was on a dual carriage way within a minute or so of leaving home.
Bearing in mind is was high 20's is this normal? My basis for comparison was my old 1.9 tdi taking much much longer.
 

abyrne153

Registered User
Its hard to tell from the video. I thought I could hear it in the second part and it sounded a bit like an exhaust manifold blow or maybe an injector seal. Possibly even a loose or damaged glow plug or a sticking valve maybe? Its nearly impossible to try and figure out something like this from a video. If you are able to get your car to Chris Adams - (adamss24 on this forum) - he is very very good on these v6 tdi engines and I have no doubt he will get you sorted.
 

LayerzA3

Registered User
Cheers - yea funnily enough have spoken to Chris about the car as it used to belong to an owner on here.

First thing - I've solved the low power issue! I've been replacing all the return lines, vac lines, clamps etc... as a matter of course and rather then doing it in one hit I've been doing bit at a time.
Turns out the issue was a jubilee clip that had some slip in it, car it transformed without the boost leak! I still actually have a few to replace but pretty sure that's power 99% covered now.

On the noise resolution I'll plug on with things and see where I get to as I've already reseated the injectors with new seals, I'll try and get some better audio at somepoint it's one of those odd things with phones they home in on road noise tons (and go pros with external mics).

I think the exhaust manifold it worth looking at in due course as I have read that before, also that bad injectors clattering can make that noise.

I might start a build thread too as long term I'd like to make more power with this car but it will need new injectors so kinda covered off a set for rebuilding today picking up a complete spare engine and gives me spares should I need them and investigation routes.
 

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adamss24

Registered User
Glad to hear you've sorted the low power issue... I cannot fault it from the video, it pulls nicely... personally I think it's an injector clattering or could be a dry tappet/hydro lifter...I wish I knew you wanted an engine, thrown a working AYM 155 Bhp at the local scrap yard, you could have had that for free...
I would have looked for a later cam roller type engine, you could have swapped the whole engine or just the cyl. Heads.
 

LayerzA3

Registered User
Glad to hear you've sorted the low power issue... I cannot fault it from the video, it pulls nicely... personally I think it's an injector clattering or could be a dry tappet/hydro lifter...I wish I knew you wanted an engine, thrown a working AYM 155 Bhp at the local scrap yard, you could have had that for free...
I would have looked for a later cam roller type engine, you could have swapped the whole engine or just the cyl. Heads.

Cheers Chris - I've never had this type of boost leak before and in VCDS it was making boost but later then requested so dismissed a leak especially as when I've had them before on my last car is was an all of nothing type of leak.

The engine was pretty cheap and was a complete unit (minus turbo) with injectors and manifolds, it will let me swap injectors around to see if that's an issue or ever swap/check manifolds.

I wasn't looking to swap the engine and still don't think I am but the spare is handy for fiddling/learning etc...

If it is the tappets I could swap the heads and swap my cams onto this head, but would port match the heads and manifold to the gaskets and clean things up a bit - nothing too major as I'm neither skilled or brave enough.
 

adamss24

Registered User
Thumbs up ! That sounds like a plan ! There is a lot to gain from a bit of port matching but the real gain is removing the bumps/swirl ports around the intake valves...
 

LayerzA3

Registered User
Slight update and plans.

Performance is better but still hit and miss - might be fairer to say I get 90% performance now where before was 70% when I fixed the boost leak - few more bits to check over on the pipes as occasionally it runs like it has another 20-30bhp.

Re the noise - pretty sure it's the tappets so taking a 2 or even 3 sided approach to dealing with this.
1 - have put some hydraulic lifter treatment in - will do 2-300 miles over the next few days to see how that gets on.
2 - I will be a diesel fuel flush on the oil - thinking a litre - run the engine for 15-30 mins then drain the oil.
3 - will add new cheap synth oil and engine flush - run for 15 mins then flush and filter change and add 507 spec fully synth oil.


If this quietens things I think I can look at lifters which plugs into the rebuild head idea above and take this engines good cams and I'd expect the noise to come back.

Jumping back on performance I've also just done an oven clean on the turbo - turbo is certainly coked up a bit but actuator moves nicely, I found it easier to pull the downpipe off (after splitting a problem nut) and getting the cleaner in that way. I'll have to report back on this and might need to pull the turbo for a full clean of the VNT vanes.
I probably should make a thread for the car actually for bits like this as it's leading into pulling the exhaust to decat it too.

Slowly but surly the car is getting there
 

LayerzA3

Registered User
Right progress - noise - mega engine flush didn't sort it (diesel oil change, engine flush and then normal oil change) - I have another project car that when running means I can get into the heads to look at/sort the tappets.

Loss of power:

I've checked the intake manifold to get the egr butterfly (though EGR is gone) - that was fine.

The two intake hose clamps nearest to the turbo slipped - these have been replaced and I've seen improvements BUT the car is still a bit Jekyll and hide.
The difference in power must be 30 bhp but the common thing is the car runs better once warm and once it's been running a while. I've pulled logs before and typically it looks ok with the N75 duty cycle seeming to lag.

I have 2 or 3 theories, the likely one - the MAF is on the way out and the heat helps the connections is they are poor.
The others - cat is clogged (have looked at this with a inspection camera so seems unlikley but I have no reference for comparison) but that's getting gutted anyway. The VNT/Actuator is coked up or has seen better days (also doubtful as I've oven cleaned this and had good movement).

My next step to test the MAF theory because they are not cheap is to try contract cleaner and the MAF Diode hack. If either of these give a positive result will go on that!

Again documenting as the 2.5's do seem to behave a bit different to the 1.9's when it comes to trouble shooting - the problem is I might of just overthought everything when VAGCOM made the MAF look good, I've been here before when they are intermittent.
 

LayerzA3

Registered User
OK I think it's the MAF, I've cleaned it twice and it gets better for a bit.

EuroCarParts sell HAS £80 (with code) & Denso £120 with code. Need to speak to Audi to see what their cost is.
 
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