17705 - pressure loss between turbo and throttle valve,

[Mk1 banana]

Evenin' all. I'm new here. So hello everyone,

I apologise in advance...

17705

The usual code I've read numerous threads on. But all seem to be different from my readings...

In short, what I've done to the car:
Swapped n75 for a 'working' secondhand one
Some vacuum hoses replaced
Cleaned and reset throttle body
(Inc new tb gasket)
Cleaned turbo out with wynnes turbo cleaner
Bypassed n249 (off the inlet manifold, t piece in vac line that runs to n249) (stop plugged in and hosed up, blanked the hose that should go to recirc valve
New split recirc valve (fmdvspltr)
New coolant temp (ect) sensor
New thermostat
New cambelt and water pump
Swapped maf for an almost new one off my other car(bora)
Checked the pancake pipe to boost pipe hose's 'o' ring
Noticed intercooler and top hose slightly oily, but think that the problem would be more consistent if there is a leak??

It's running better now but I'm still not happy with it and code is still present...
the car felt pretty good at first, once in the first week of ownership it felt like it randomly decided to dump its boost under half throttle, (still under load)
I assumed (wrong!) it was just the way I drive it, but it progressively got worse. To the point it done it at about 4000rpm with full throttle,
I also noticed (after fitting a cone filter) it sounded different, most times it 'dumped'
I was lead to assume it may be the n75 or recirc playing up, I swapped the n75 for a mates one, which he didn't need as he has a manual boost controller, (when he last used it it was ok?)
No difference, fitted a new "fmdvspltr" forge splitter, better but not fixed, then I bypassed the n249, again, improvement, but not fixed,

Also, it's probably worth noting, it intermittently lacks boost, and is NOT dependant on engine coolant temp,

Sometimes there Is not a 'dumping' noise even when it feels like boost is normal pressure,
Sometimes it even feels like there is no boost at all,
I'm wondering if something, somewhere is wrong so the n75 is dumping before the split recirc valve, it does sound like its letting go of boost pressure from the n75,

I've heard a mention of the 'bug' that affects the ecu's ect reading so it stays in cold start mode at times?

I would love to find this problem and fix it, help would be seriously appreciated!
I'm an underpaid mechanic, and do not have access to vag-com...
So diagnosis is getting long winded!
thanks in advance,
Reece

 

[RICKY3]

Is your split r set to fully recirculate? And what dv was fitted before the split r?


Sent from my iPhone

 

[Mk1 banana]

Hi Ricky, it's still pre set from the shop I got it from, which is still split, it was running the standard/ oe recirc valve before I replaced it, seemed a little better at first, but gradually deteriorated as with most other attempts at fixing it...?

My other thought, is, if I've bypassed the n249/ boost control valve. Maybe the n75 is over reacting due to lack of response from the n249 (which is still fully connected except the recirc end is blanked off)?

 

[RICKY3]

I would try it with blanking plug on an see if that makes a difference as my own lc runs so much better with the split r set to fully recirculating


Sent from my iPhone

 

[LEE69]

Try a standard dump valve see if it goes.

 

[aviaa25]

Did you check your breather pipes and valve under the intake mani?

 

[nd-photo.nl]

+1. This will most likely be the culprit. I've had the same problem and had it fixed just recently. First thing to do: use the blanking plug for the Forge Splitr and get the error fixed, if you want use the trumpet again later on.

Check all connections between turbo and trottle body. Check list:

-Boost pipe to pancake pipe
-pancake pipe to intercooler
-intercooler to throttle body
-vacuum hoses under the inlet manifold (double check these)
-vacuum hose lower breather pipe
-crankcase breather pipe (Y-pipe)
-PCV valve (replace if necessary)

The one under the inlet manifold is most likely to split, causing it to suck in dirty unmetered air.

My error has been fixed after checking all these things on my list, cleaning and adapting the throttle body and replacing the n75 valve (which you ave already done).

Remember: the errors dont erase themselves, you need vagcom to do this.

 

[ibizacupra]

smoke test it
any leaks will show themselves

it may save you some ££ from not having to do the the poke and hope approach on randomly changing stuff

 

[Mk1 banana]

I've blanked the atmospheric port on the split r,
And re connected the original vac line to it, then blanked my new one (just incase the n75 was overreacting due to no response from the n249)
It feels better when it's NOT playing up, but she's still losing boost intermittently?
Sounds like it may even have a leak now? But only since yesterday?

I'm not sure of any one local who can do smoke (leak) tests, any one recommend any where? I'm from hastings, e.sussex...
Thanks for your help, so far guys
Reece

 

[richie kaye]

Im in the Same boat code wise

Great read on your attempts so far,youtube a smoke test on the system

Im getting this done so I can find the culprit without seriously forking out
Gotta be a boost/vac leak,im getting a kind of loud induction noise and hardly any turbo unless I open it up on full throttle

Will keep an eye on this post to see your findings

 

[Mk1 banana]

Mines the other way round, at times, I get full boost most times and boost runs out way too early, I've been told it should boost upto (around) 500rpm before redline. Mine runs out halfway there if I use full throttle, and sometimes doesn't boost up on throttle after, but mostly it does, for a short period again...?
Will look at the leak test vid(s) later mate, thanks for the idea, i didnt eveb thibk to see how it works...
I might have to resort to the old fashioned way, tyre valve and compressor, easy enough for me, I just need to work out what to blank out (PVC etc).....

 

[Mk1 banana]

Im in the Same boat code wise

Great read on your attempts so far,youtube a smoke test on the system

Im getting this done so I can find the culprit without seriously forking out
Gotta be a boost/vac leak,im getting a kind of loud induction noise and hardly any turbo unless I open it up on full throttle

Will keep an eye on this post to see your findings

Are you getting a noisy hissing noise on acceleration?

 

[richie kaye]

Yeah under part throttle,coming from pass side
Tryin to drive off boost as much as poss because its really lagging

Garage next week for a test me thinks

 

[Mk1 banana]

Is yours a Cupra r?
I think it's only the k04's boost hoses and pipework go near that side, if yours is a Cupra (180) you'll have the k03s, the hoses for which are central to offside front wheel arch (for intercooler etc)
If its that noisy, it 'should' (he says lol) be a visible split in a hose...

 

[supersticky]

I had this problem and went though the book but in the end it was just the maf reading wrong !! Changed now all sorted running lovely

 

[Mk1 banana]

It's one of those annoying codes, that could mean almost anything!
I did try another maf, If only it worked!

 

[richie kaye]

Is yours a Cupra r?
I think it's only the k04's boost hoses and pipework go near that side, if yours is a Cupra (180) you'll have the k03s, the hoses for which are central to offside front wheel arch (for intercooler etc)
If its that noisy, it 'should' (he says lol) be a visible split in a hose...

Ive got a mapped ko3s,So all the hissing could be down the front of the One side mount IC?
Seem tight to acess that area

Went to garage to ask about the Smoke test,he wasnt interested so need to find one that will

Im a Dj so I have the dogs of a smoke machine,but dont wanaa put any old smoke through the intake
It smells of strawberry though lol

 

[LEE69]

lol

They pressure it to about 15 psi anyway

 

[richie kaye]

lol

They pressure it to about 15 psi anyway

Saves me getting it out and smoking the street out and the neighbours calling the fire brigade

 

[Mk1 banana]

Latest update, chaps, I fitted a boost gauge, I'm running 0.5-0.8 bar, still got the code, an feels like a lack of boost at times, dispite being within parameters, it's an odd one :s

It does like to hiss/ whistle (most times) under acceleration, I'm thinking possibly a slight boost leak, and n75 doesn't like it... It sounds like its dumping boost, before the recirc valve gets a chance...