Hi all, I recently purchased a MK4 GTi 1.8T (AUM)and I am after some advice. It was a short 60mile trip back home with the car and it drove faultlessly for about 30 miles. Then I noticed a lack of power and a rough idle. So I hooked my scan tool up and found a fault code 17705 pressure drop between turbo and throttle valve. I erased the code and it drove fine since. So I started looking today to see what I could find I listened out for any vacuum leaks and all sounds good. I sprayed brake cleaner around all the vaccum pipes and breathers to see if the idle picked up and nothing. Then I took the DV off and and Vac checked it and it holds the vaccum fine. So I would really like some assistance as to me it seems Electrical possible n75? Also on a cold start I hear what sounds like a air leak for about 20seconds but I believe this to be the SAI kicking in? Any help would be great Cheers
Sounds like a pcv or boost hose fault. This page shows the pcv system and parts that fail. It Probably didn’t show up with brake cleaner spraying as the split pipes would seal ok under vacuum but leak under pressure. http://r-techperformance.co.uk/customer-pre-booking-checks-1-8t-20v/
https://www.clubgti.com/forums/index.php?threads/20vt-boost-and-injector-leaks.287628/ Also take a look here
Thanks for the help. I did notice earlier that one of the PCV hoses had oil residue around it but couldn't see any splits anywhere. Are there aftermarket options for replacing these PCV hoses?. Am also going to do a n249 bypass at some point. What diameter vaccum pipes are used on this engine? Would check but car is at work ChersC
As above I'm still trying to track down a leak on mine that is on the same code. Can you hear any whistling as you go past 2K? The SAI is pretty noisy. Sounds like the exhaust is blowing perhaps exacerbated by the large exhaust/inlet overlap on warm up too. I also though it was the cat heat shield vibrating as the rear studs commonly rust off. Things I've done on mine are put a new seal and socket on the connection that leads down from the turbo into the pancake pipe. No oil appears to be getting past the seal now so I think this has been an improvement though not the issue. This is the AUM breather arrangement 13A & 9A have already been replaced on mine, but 10 (06A103221BK) was original and split. I bought a cheapo leak down tester and whilst I've managed to pressure test from the pancake pipe>charge cooler>throttle body hose with a tyre inflater as it held pressure. The full system leak test is going to require a compressor.
No whistles past 2k for me. Is that pipe which is highlighted in the pic the pipe which is under the inlet manifold and is secured by the metal spring clips that VW use for intercooler pipes etc?
Yeah mine was still on the OEM oetinger single use clamps which were loose as the pipe had softened. Measuring off the replacement topran pipe one end is 14mm the other is 19mm. Not sure what it swells to fitted as it's still in the packet, but Norma 10-16 & 16-28 worked fine on the repaired pipe.
Thanks for the info. Do you know anywhere that sells the whole PCV system /silicone upgrade kit . Cars on 150k so might as well replace all these components. Also are you aware of the stock vaccum hose internal diameters? Noticed what looks like chaffing on the pipe on the top of the DV . Probably not helping
There are loads of aftermarket kits on ebay no idea on the quality. I just bought that single pipe from B & B although I might need the t piece (5) as well. The valve (6) might need replacing on yours. As for silicon the replacements the pancake pipe I got from creations motorsport was not really pattern at all and so stiff it was never going to fit.
Is the pancake pipe not the one from the intercooler>turbo . Have heard about creations motorsport not being a direct fit . But it's over £200 for a direct bolt on I believe
Yeah in that region. It's the hose before the pancake pipe socketed onto the back of the engine down pipe.
Also how quickly do you fiind your 1.8T to get up to operating temperature? I had a polo before which would get up to temp fast . But my golf seems to get up to temp really fast not overheating just gets to opersoper temperature within about 5-10mins on idle. Checked the temp on live data and they're is discrepancies between my live data and temp gauge which I have heard is normal. Just wondering if it's just a 1.8t thing .
It's a lot quicker than my Mk2 8v GTI ever was. Sucking exhaust back into the inlet during the extra overlap in the cold phase has to help with that plus forced induction. I don't know how they compare to the earlier non VVT AGUs for warm up.
