Lack of power once hot

[Leigh a4]

Hi all im new to audi ownership iv recently purchased a 2007 a4 2.0 tfsi quattro with 137k full history mostly audi

The car was running cool which has now been sorted by replacing the thermostat

I noticed it was a little down on power beforehand but after having the thermostat replaced i have noticed that once it has been up to temp for around 10 minutes there seems to be no boost at all

Midland vw diagnosed it as faulty dv,which i have had replaced today.I was excited to pick it up today and find a whole lot more power but sadly that wasnt the case

They have told me that the intercooler has a small leak so although it is boosting better it is not running as it should

On warm up it seems to drive so much better than before lots of power but as soon as it has been hot for 10 mins again it is just gutless,i would say it is the equivilant of a 1.6 NA engine

So my question is could a small intercooler leak make all the power go once the car is hot or am i looking at a number of issues ?

There are no codes being thrown due to this fault

Any help would be much appreciated

 

[Leigh a4]

Well cheers guys

 

[Baka]

Hi ya, I'd start by making sure the car is boost tight. It'll be easier to diagnose any further faults once you know there's no boost leaks.

 

[Sidrick]

You've been told what the issue is. You've a hole in the pressure side of the intake, it's likely expanding as it heats up.

 

[Leigh a4]

That is all i was asking if anyone thinks that the intercooler is the only problem as i wanted to prioritise the repairs on it

 

[Charlie Farley]

Ideally one should run vcds and see what errors are logged , then work from that point.
A failed or failing DV will not show on the dash anyway but will leave data in vcds to indicate it , as will other problems.
Leaking intake and pressure lines will also show up via vcds as there will be other issues connected to them.
A basic diag will only show basic info , vcds will give far superior data and fault logging , i'd be running that to pin point whats going on rather than second guessing what the problem is.
Just my input really .

rob

 

[Sidrick]

That is all i was asking if anyone thinks that the intercooler is the only problem as i wanted to prioritise the repairs on it

Sadly you can't get an answer on this from an internet mechanic, and probably not a realy life one either. Gotta fix that leak then see how it looks. Plenty second hand intercooler around, or you could maybe bypass it completely for test purposes before spending money.

 

[Leigh a4]

You've been told what the issue is. You've a hole in the pressure side of the intake, it's likely expanding as it heats up.

Turns out it hasnt made any difference having had the intercooler changed.which is why i asked the question to begin with.

After the car has sat warm after a drive once started again it is lacking power but once on a run and is cooling down the power comes back so something is getting hot and causing this any ideas ?

 

[i3oricua]

Turns out it hasnt made any difference having had the intercooler changed.which is why i asked the question to begin with.

After the car has sat warm after a drive once started again it is lacking power but once on a run and is cooling down the power comes back so something is getting hot and causing this any ideas ?

You need to find someone that can run a diagnostic on the car or you’re just throwing money at it. We’re trying to be helpful here but opening your wallet isn’t going to fix it without knowing what you’re trying to fix. There’s likely an error code trapped in the ECU that might direct you to a better solution. I don’t know what could cause that specific problem since I’ve never heard of an issue like this. If you’re dead set on throwing money at it and buying parts then try changing the coolant temp sensor located on the back of the block. It’s a £20 part and take a few minutes to change.


Sent from my iPhone using Tapatalk

 

[Charlie Farley]

As above really and already mentioned, get VCDS run on the car and go through the error log, realtime data logging will help aswell, you are very unlikely to find the core problem by guesswork alone, these are very complex systems and need proper diagnostics to check the system out fully.
Cheaper to get it diagnosed properly than just second guessing and spending on parts you maynot even need, let alone solve your problem.

 

[Leigh a4]

Yes it is booked in to get this diagnosed.Im not just throwing money at it,it obviously needed the intercooler diverter valve and thermostat replacing and i got the car cheap so i dont mind spending abit to get it running spot on.

But the intercooler could have waited and i had this disccusion with midland vw about me doubting this being the issue but it sounded like it may be expanding the leak once hot.he said he was 90 % sure it would be the intercooler.They obviously have vagcom and can run live data on it which it looks like they are going to do again.If an audi vw specialist cant diagnose it correct first time what else could i have done i thought they knew what they were doing to be honest.

I spoke to the guy on the phone today and he has said that its possibly the cat as he has seen this kind of fault a few times with no codes logged at all and it was the cat but im not going to be jumping into getting that job done as its expensive as you may well know.

Im not sure how long it was running with the thermostat stuck open and with the intercooler leak so maybe it has been running rich for a while and this has killed the cat but i will keep it posted as it may help others in the future who experience the same issue

 

[Charlie Farley]

If by some chance you do need a new cat , drop me a pm as I have a good low milage one that may be of help to you.
Not using this as a means of selling it as its in classifieds anyway, just a heads up really if you need something.

 

[Charlie Farley]

You should ask them for a copy of the log when they first ran vcds.

 

[Leigh a4]

If by some chance you do need a new cat , drop me a pm as I have a good low milage one that may be of help to you.
Not using this as a means of selling it as its in classifieds anyway, just a heads up really if you need something.

Its going in on tuesday so if it turns out to be the cat i would definitly be interested in buying yours pm me what you want for it please mate and il be sure to ask for the log this time

 

[Charlie Farley]

 

[Leigh a4]

You should ask them for a copy of the log when they first ran vcds.

Just to update

Car went in today they were confident they would find the fault but later they rang and said they need to take the cat off to check if it is blocked and it would be £180 to check and refit

Asked for the logs they said that nothing is coming up on the diagnostics and that nothing came up for the diverter valve nore the intercooler

It is a real headache to have to buy a cat when it may not actually be the issue.If i dont have a cat to replace mine and its shot then it would have to be put back together and then pay again to have a new one fitted

Is there no way of testing when the cat is clogged without removing it ? And does it sound right that there would be nothing on the diagnosis for a faulty diverter and a leaking intercooler?

 

[Charlie Farley]

If they cleared the faults last time then the only way to see what faults were is if they saved a copy of the previous vcds session, if there were any faults logged..
Real time data logging will show up how the engine is running , boost pressure etc , also other engine parameters whilst the engine is running.
A failing DV wont leave a specific fault but will leave other indictors , same with air leaks.
Inter coolers wont show up a specific fault either but a leak will show up if the person doing the diag knows what they are doing and looking for.
sounds like they are just running a normal scan rather than doing specific diagnostics in real time to check specific area's for malfunction , which is what the diagnostics it meant to be used for, to look at specific areas to see if they are running correctly .

 

[Leigh a4]

Yes that is what i think is going on and im not filled with confidence by some of the things they say.I think i need to find another specialist to look at it.The only thing im unsure of is that if the cat were clogged surely it wouldnt pull strong for the first 20 minutes as it would be causing back pressure from cold it doesnt seem to lag until its been at 90c for about 10-15 minutes.Then it is as though the turbo is just not spooling at all.I have checked the MOT history and it failed on emmisions from lamda reading at fast idle but was then passed so its possibly down to the cat although.I think im going to have to take it elsewhere to confirm the fault

 

[Charlie Farley]

Just a mad thought chap, possibly a poor electrical connection on the DV, it has been known that the dv is replaced and the plug doesn't get refitted or becomes faulty, thus the valve doesn't function correctly.
Also when you say after being hot for 10 mins it seems gutless sounds very much like heat soak.
I personally would be getting it diagnosed properly to pin point where the problem is , not just a standard scan.

 

[Leigh a4]

Sounds like a possibilty mate would be an easy check to start with.Theres another vag specialist nearby so il.give them a call.would have thought an audi vw specialist would have vag though maybe they dont.Iv read that the n75 valve with a split hose gave someone similar sympthoms but as you say it needs diagnosing properly.Oh the joy of fixing cars cheers for your help pal il keep you updated as i may well need that cat