bought the car some time ago, was running brilliant. CEL came on recently so i checked for error codes, turned out to be a CTS error, changed it, no errors since.

i'd like to mention that i drove the car for about 1 month with the CTS error... (if that makes any difference here)

starting at ~half of that particular month i found the boost to be kind of missing. checked all the visible pipework as i changed the CTS, found a split low breather pipe, fixed it for the moment. problem was still there.

the facts:

-power output till turbo kicks in is solid, although idle rpm is 720-740

-turbo kicks in the moment it should

-turbo sounds as it should

-no smoke or anything like that

-no boost gauge installed

-car is running a standard map (factory)

i'm planing on checking the DV tomorrow if i find the time (although i'm not sure i'll be able to tell if it opens or closes to slow, or gets stuck in between).

i was thinking about the N75 as well, but the method of testing i know about (wastegate hose disconnected) would require either a boost gauge or knowledge of the moment/rpm level at which the valve would open the wastegate so i won't rev above that...

any hints or suggestions ?

Edited 22 April, 201214 yr by za_killer

bought the car some time ago, was running brilliant. CEL came on recently so i checked for error codes, turned out to be a CTS error, changed it, no errors since.

i'd like to mention that i drove the car for about 1 month with the CTS error... (if that makes any difference here)

starting at ~half of that particular month i found the boost to be kind of missing. checked all the visible pipework as i changed the CTS, found a split low breather pipe, fixed it for the moment. problem was still there.

the facts:

-power output till turbo kicks in is solid, although idle rpm is 720-740

-turbo kicks in the moment it should

-turbo sounds as it should (the paranoid me would say it sounds sometimes more quiet)

-sometimes (may be my paranoia again) on cold starts, i do feel like the boost is partially (or totally) back for ~1 min.

-no smoke or anything like that

-no boost gauge installed

-car is running a standard map (factory)

i'm planing on checking the DV tomorrow if i find the time (although i'm not sure i'll be able to tell if it opens or closes to slow, or gets stuck in between).

i was thinking about the N75 as well, but the method of testing i know about (wastegate hose disconnected) would require either a boost gauge or knowledge of the moment/rpm level at which the valve would open the wastegate so i won't rev above that...

any hints or suggestions ?

i have had this problem for about 6 months now! i changed the n75, dv, maf and made sure the turbo to intercooler pipe is air tight. i have also done the n249 bypass but still is it not right. i found a few cracked hoses and have replaced them! i have now given up tbh

forgot to mention, unplugged the MAF, no improvement...

sorry to hear that pokerdemon

forgot to mention, unplugged the MAF, no improvement...

sorry to hear that pokerdemon

crap aint it lol! does yours surge when yo boot it? I have read hours of the 17705 fault and tbh, i dont think anybody has actually solved it? Unpluging the maf thing did nothing for me either but i bought one anyway. Its the mass of crap hoses in there, it will be a pinhole crack somewhere probably!!

no surge, no error code, nothing...

got into my car this morning, boost seemed to be somehow there (i do feel a kick as the turbo kicks in), but it's not like it used to...

makes me sad... or rather angry...

I know its been said before but go over all the boost pipes and vac lines again.

I had the same issue aswell not so long ago, was very loud felt sluggish etc and it also made crap figures on a rolling road. In the end i had a tiny split in one of my boost pipes which i replaced and the car seems to go alot better now and its alot quieter.

can you remember which one of them had the split ? was it a hose or a pipe ?

my patients is reaching it's limit on this one and i'm going to change all the hoses one by one if nothing turns out pretty quick...

I have had the y breather pipe at the right hand side of the rocker cover split, and also the two under the manifold.

Check the 2 under the manifold i know its fiddly to get at but you need to have a good look and feel as the splits can be quite small. I replaced all these with silicone pipes from creation motorsport and the car runs alot smoother now.

If you want you could fit a oil catch can to eliminate all most of the pipework, mark (bowders1) has a good write up on here about fitting a catch can.

update

so i've made myself a DIY pressure tester (2.5 pipe with air valve).

removed puck valve, plugged the hole, connected the leak tester to a car 12v compressor and turned it on.

found a pipe under the mainfold not tight enough, fixed it. no further leaks to be heard.

the thing is:

1. compressor gauge never goes above 5 psi (thought of a dodgy gauge, not sure about that, maybe it's just not sensible enough at low pressure)

2. no further leaks are to be heard

3. pressure holds for short term (turning off the compressor and leaving things for about 30 secs untouched => there's still pressure in the system)

4. if i leave the system pressurized for more than 2 min, pressure drops to 0 (unable to tell at what pressure the system is when pressurized cause of the gauge)

the upside:

1'st gear acceleration has improved noticeable (btw i changed the breather pipes a couple of weeks ago for oil resistant silicone ones)

the complaint:

still missing the kick in 2'nd as turbo kicks in

should i go for the N75 next ? or am i missing something...?

Edited 28 January, 201214 yr by za_killer

I have had the y breather pipe at the right hand side of the rocker cover split, and also the two under the manifold.

Check the 2 under the manifold i know its fiddly to get at but you need to have a good look and feel as the splits can be quite small. I replaced all these with silicone pipes from creation motorsport and the car runs alot smoother now

Sorry stupid question,.but.do.you.have to remove the manifold.to get at these pipes. As I am getting similar and I can here turbo quite loud and it drinks petrol like there is leak too so.want to check everywhere. But also not sure what pipes.are which as never had a petrol.turbo before.now.

fit a boost gauge or log actual and requested boost on vag com

no point go around in circle if you dont know what these are to start with.!!!!

atleast you can give us an idea then what its doing and we can prob tell you whats wrong ;-)

Sorry stupid question,.but.do.you.have to remove the manifold.to get at these pipes. As I am getting similar and I can here turbo quite loud and it drinks petrol like there is leak too so.want to check everywhere. But also not sure what pipes.are which as never had a petrol.turbo before.now.

no manifold to be removed. just the metal tray in front of it (2x hex + oil dipstick + a sensor to remove)

fit a boost gauge or log actual and requested boost on vag com

no point go around in circle if you dont know what these are to start with.!!!!

atleast you can give us an idea then what its doing and we can prob tell you whats wrong ;-)

was on my to-do list after the pressure test. only one issue bout it: i do have a cable and the necessary software but my laptop's battery is dead so i'm left with 2 options:

1. sort a new laptop and go for a spin

2. do things in front of the house

will logging values without actual road rolling be of use ?

Doesn't matter if you log the values on a real road or on a rolling road. If requested boost figures are low then there's something wrong with your ECU or map, if requested boost is higher than actual boost then there's something wrong with the turbo control system which is either going to be:

- Leaking boost hose (which you've ruled out)

- Split vac hose (which you've ruled out)

- Faulty DV, N249 or N75

- Sticking wastegate or wastegate actuator

- Knackered turbo (although you'd see smoke and it would sound awful)

Out of interest what fuel do you run it on? It's nothing to do with the turbo but I found repetitive use of normal 95 Ron made my car really sluggish.

Doesn't matter if you log the values on a real road or on a rolling road.

....

Out of interest what fuel do you run it on? It's nothing to do with the turbo but I found repetitive use of normal 95 Ron made my car really sluggish.

thanks, my only dilemma here was whether the wheels have to be in motion or not. i now need to sort a laptop to do my job, as doing this on my driveway clearly won't work

btw i've also tested my DV and the membrane holds as it should (besides, the tschhh sound on throttle lift is and was always there)

next up: boost figure log, n249 command check (whether vacuum and boost is there as and when it should). given the results of these 2 i'll see what comes next.

i quit using 95 long ago (same reasons)... 98 or higher it is for me (depending on the gas station).

N249 bypass scheduled later this day, as the feed leading to the DV only gets vacuum (no matter how high reved)

Let us know how you get on.

While you've got the metal plate off which the N249 fits to the bottom of, double check every one of the vac pipes coming off the inlet manifold for splits (I know you've probably checked them already?)

While you've got the metal plate off which the N249 fits to the bottom of, double check every one of the vac pipes coming off the inlet manifold for splits (I know you've probably checked them already?)

pipes are pressure checked, so no doubt they'll hold.

did the n249 bypass (spliced the pipe leading to n249 with one leading to the DV, blocked the old DV pipe)

i'm not happy with it... no improvement whatsoever. even tried leading a direct pipe from the IM to the DV, blocking the n249 feed...

my concern lies in the following fact:

-car in neutral, idling, vacuum in the DV control hose (as expected)

-car in neutral, revd at 3000 ~ 3300 RPM, still VACUUM in the control hose of the DV (despite the n249 bypass) (shouldn't there be boost ?)

can't log the boost values, as my china-vagcom-cable broke down...

That does sound a bit odd. With the throttle open and the turbo boosting, the vac hose between the manifold and DV should be pressurised but when the throttle closes the inlet manifold develops an instant vacuum which would open the DV. If the there's a vacuum in that hose already then the turbo isn't pressurising the air or the boost is leaking out before the manifold (or out through one of the other vac hoses connected to the manifold).

I know it's probably not easy if you've got a pressure gauge in that vac line which you're looking at, but have you tested it with the engine under load (i.e. in gear)?

edit: pressure drop anywhere in the pipes seems unlikely (pressure tested them a couple of days ago)

i'll reexamine the pipework, sort some things out...

if that still won't fix it, i'll splice the DV feed to the interior of the car and check it whilst driving...

the needle in the haystack approach rapidly looses it's effectiveness here...

Edited 1 February, 201214 yr by za_killer

i've been at it again:

-got the metal plate off

-cleaned the n249 wiring with contact spray

-sprayed some cleaner into the n249

-fixed everything back together

test runs:

-ran a hose from the DV control hose (t-piece before the DV) inside the cabin

-test run 1: n249 bypassed: pressure coming out of the test hose under engine load (in gear, rolling) -> a good sign

-test run 2: n249 connected again: at ~1800 RPM pressure starts to replace the vacuum

my guess is the n249 was gummed up, cleaning it fixed the problem

so i'm now standing in front of a car starting to boost at around 1800 RPM.

i know for certain that the pipes are not leaking (pressure tested)

i know for certain that the DV holds (membrane intact, i've tested it)

there are no recorded faults

i now have a working n249

a boost gauge (or vag-com boost record) would have been massively helpful, but i incline to say that the wastegate is not stuck or sticky

that leaves me with 2 options:

n75 defect (dunno how heavy the impact on the performance would be)

throttle body needs realignment (?) (as idle is a bit rough for my taste) -> TB has been cleaned about half a year ago; problems started showing up only 3 months ago

Ok so that rules out the N249 being a problem, and boost starts at about 1800 revs which it should.

It sounds like the turbo is coming in as it should but just not producing the boost it should be.

Are you able to use the gauge you used to test the DV vac hose as a boost gauge or does it not have psi/bar measures on it?

Next step is N75 testing. Ideally you could do with a Briskoda member (or any 1.8T owner) near you who can lend you their N75 for a quick test. If the N75 is duff then the turbo will be spooling up as usual but the wastegate will be opening straight away (or sooner than it should) so it's not getting up to the requested boost. VAG-Com would easily show this as a difference between req. and actual boost.

I wouldn't have thought the TB is a problem - they take years to get coked up once you've cleaned them. Again if you can get a copy of VAG-Com you can do the TB reset and see if it helps.

i haven't used a gauge on the n249...

progress:

-checked inner resistance of the N75, was ok (somewhere around 35 ohm if i remember correctly with engine being hot)

-checked power supply to N75 with engine running (voltage between pins around 12~13, pin 1 to ground 18~19, pin 2 to ground 5~6)

-took off the hose leading to the actuator and tried blowing air into it -> hose not leaking, but i didn't manage to blow strong enough to get the actuator moving (knowing a human can usually blow around 2 psi at atmospheric pressure i even doubt it's possible for me to move the actuator without mechanical aid)

unfortunately i've nowhere to sort a N75 for a test ride, so i'll:

1. clean the N75 insides, test it on a 12V supply (should hear the clicking)

2. spray some W40 like substance on the actuator (eliminating the possibility of it being lightly-stuck)

3. if nothing happens: buy a N75 and slam it on

Edited 2 February, 201214 yr by za_killer

Good plan.

The vac hose between the inlet manifold and the N249 (or between the inlet manifold and DV when you bypassed the N249) would give a boost reading at open throttle if you were to tap into it with a boost gauge. Might be worth just buying a cheap boost gauge for testing the actual boost on that hose if you haven't got VAG-Com (or tap into the fuel pressure regulator as you would with a proper boost gauge install)... you could always fit the gauge into the dash properly in future or sell it on.

You might be able to get an N75 cheap off of a 1.8T car at a breakers, brand new they're about £40

thank you chicken_eyebrow for your support so far

update:

-n75 cleaned and tested -> working (dunno how bad it was as i've cleaned it prior to testing)

-actuator cleaned with rost off and degrip oil

i'm still waiting for the chemicals to unfold their full effect. will take the car for a drive later this day and see if i've made progress or not.