A3 1.8T AUM 8L - Boost issues

[M0onsh1ne]

Hi all,

Im new to this forum so apologies if im posting in the wrong place.

I've been having an ongoing issue for a good few weeks now with my 1.8t A3 AUM it would appear as though its making very little boost. Its like the car is in LIMP mode and constantly stays there, however If im stand still in traffic for say 10 minutes and the engine bay is getting really heated (not overheating) just getting hot, when i pull away the car runs perfectly and boosts correctly for about 20 seconds and then hits the flat spot again and stays that way. Also if i go on a run and turn the car off for 5 minutes so that its sat there heating up again, when i start the car and drive for the first 20-30 seconds or so the car performs as it should and then goes LIMP.

Things I have tried.
checked for boost leaks - upper Y crank case breather slight tear but now resolved, smoke test peformed cannot see any visible leaks.
Unplugged the MAF sensor and ran the car - no difference
Unplugged the N75 valve seperately to the MAF - no difference
Removed the boost pipe from ther N75 to the Actuator and tested the car - That feels a little better but no where near what it should be still LIMP
Tested the Stock D.v and this hold vaccum.
Connected a pump to the wastegate Actuator nipple and pressurised to se the wastegate ARM moves freely. this is a little stiff but it does open and close. However when starting the car and giving it a tiny bit of throttle the arm does not move at all. not even a little bit, is this normal?
Changed spark plugs
Tested coil packs and all are working.
I have scanned the car using a VAG-COM and the Torque app and there is absolutely NO CODES.

The thing that is bugging me is the car works for seconds at a time after it has been sitting there getting really warm at idle, so im thinking the heat building up in ther engine bay is sparking something into life for a few seconds..
Also sorry when i first start the car it really struggles to turn over, then as i try to pull away its almost stalling... this is only from cold starts though.

My car is standard with bolt on mods.
3' down pipe straight through to a ****** sports exhaust
2.0t coild packs with spacers
Creation motorsport TIP
N249 bypass with EGR valve removal.
did have an induction kit tot he front air vent but since this problem i have taken it off as its easier to work with the car so it just has a filter to the MAF at present

I would appreciate any help or advice given i have absolutely no idea what it could be

Thanks Aaron

Apologies If i have posted this thread wrongly some how hehe

 

[M0onsh1ne]

**update

I thought perhaps the wastegate was opening to soon so i tightened the nuts on the arm a few turns.

I logged the vaccum at idle as between -20 to -25 hg
When i put my foot down im making boost to 15psi but there is no delivery of the power.

The boost is there and being made but i am not getting the kick in the nuts im after.

Cheers

 

[<tuffty/>]

If your engine isn't mapped then 15psi will put the ECU into limp mode...

If its genuinely going into limp mode there will be a code... the ECU's software won't take preventative action for no reason and certainly with no code...

Its a tricky one tbh... you appear to have checked everything that is normally an issue... at this point in time it ideally needs a second set of eyes and maybe some diagnostics on the dyno to log stuff and see whats what

The fact that you got some boost from adding preload suggests it could be a hardware issue but difficult to tell without looking tbh... have seen turbos stick partially open making things laggy and unresponsive with could be the wastegate or the actuator...

If its nothing obvious then unfortunately its gonna be tricky to diagnose over the internet

<tuffty/>

 

[M0onsh1ne]

Hey Tuffty,

Thanks for the reply.

I know 15PSI is high for my car being unmapped but im thinking i got that because i pre loaded the arm. normally i think im around 7-10 roughly. so i will put the preload back to what it should be. Then i should be seeing 7-10psi figures i believe.

Getting it in to do some diagnostics would be perfect but funds are low and tbh ive had so many issues with the damn thing im starting to think do i bother anymore, its pretty old lol

I'm wondering how easy it is to remove the wastegate actuator, from what i have seen on the net a load of other stuff needs removing aswell to get to the nuts and bolts and what have you so it looks a PITA.

 

[silestanix]

Good luck sorting this out man...

 

[<tuffty/>]

Age is in the eye of the beholder my friend...

Mines a 2001 but still seem to be able to spend money on the old girl

I believe AUM K03 cars run to around 7psi as standard

K03 turbo's are easy enough to get to... easier than a K04...

<tuffty/>

 

[ben4866]

My experience of Maf failures gives the same symptoms , I still make normal boost levels but it just feels flat as a fart whenever the maf goes down.
(I run the same me7 management on my agu)

Can you not borrow a maf from someone to try?

 

[M0onsh1ne]

Hi Ben,

Cheers for the reply.

I do agree with ya there, I have been through 2 Mafs in my time on this car but each time they always gave a code so they were easy to diagnose as being up the swanny. This time... no code ofcourse

I dont know anyone with a car similar to mine to try it, that would be the easiest thing to try for sure. i do still think potentially the MAF could be at fault, I just dont want to buy a new one for it not to be the issue. when i went on a run i gave it some right beans to red line in 3rd gear and it only managed to pull if i remember correctly no more than 80 g/s. which is low, i think i should be somewhere around the 120+ g/s on a standard but i could be wrong?

 

[<tuffty/>]

Are you using genuine Bosch MAF's or pattern parts?

<tuffty/>

 

[M0onsh1ne]

Genuine Bosch, atleast the one i have on now is genuine Bosch. I had it out the other day to give it a clean

 

[M0onsh1ne]

**update

Well ****** me i've gone and fixed it.

Long story short is was the ****** coolant temp sensor!

Long story - I created some.dials on the torque app this morning and one of the things i monitored was my coolant temp sensor, which was reading 131c as i started the car.. i thought surely this cant be right.

Anywhoo i cracked on with a few other things like cleaning the o2 sensor and checking the fuel pump resistance (to do this i used a volt meter and set it to ohms, i then connected the prongs to pin 1 and pin 2 on the fuel pump itself and got the resistance reading of 1.2, i believe a reading between 1 and 3 means the pump should be all good) and making sure it was working and giving me fuel which it was.

I walk into my back garden and would you believe it my old coolant temp sensor (the black one) which i replaced for a green one over a year ago, was laying there on the stones in plain sight
**** me i said, its a sign from the gods.

With that i quickly jumped to it and cleaned the sensor up and swapped it over with the green one.

I started the car and instantly i knew something felt better. Just from the turn over. No stuttering. (Temp sensor read 40c on the torque app when i turnt her over) After idling for a while a revved her up and she felt good. So with that i went for a little drive....the ole girl is back up and running! Too well i might add.

As a test earlier i mentioned i really tightened the wastegage nuts (over tightened) to see if i had a wastegate problem, well i didnt loosen it before the drive did i... went like **** off a shovel

So im about to put the wastegate back to default (3 turns of preload) i believe is correct?
Cheeky question, could you tighten it more than that? Or will it cause damage? Obviously it felt great on the test drive so i wanted to try and get away with as much preload as safely possibly.. because im greedy

Just wanted to update you all incase anyone comes across a similar problem thankyou all for your help.

Cheers Aaron

 

[<tuffty/>]

So im about to put the wastegate back to default (3 turns of preload) i believe is correct?
Cheeky question, could you tighten it more than that? Or will it cause damage? Obviously it felt great on the test drive so i wanted to try and get away with as much preload as safely possibly.. because im greedy

If only...

Couple of things... ECU will go into limp if it spikes too much and can no longer control boost...

Rods... K03's are spiky torque delivery at the best of times... doing this to the actuator sets a higher base boost and ECU won't be able to control it properly without being mapped to suit...

Correct tension is three turns from closed... stick to that dude...

<tuffty/>

 

[M0onsh1ne]

Yo tuffty,

if u dont ask u dont know right?

Roger that, i have put it to 3 turns and left it as that i dont want to damage the car just thought i would check

I'll stick with that

Cheers dude

Aaron