1.4 Twin Charged troubles

[voca]

Hi All


Appologies in advance, this is a big read.


Car: 2008 Golf MK5 GT Sport 1.4 Twincharged 6 speed DSG. 130K on odo. Full VW dealer history until 120K in books. Previous owner from Geelong Vic.

Problem: Engine idles and revs freely but under load boost swings to max, engine chokes on excessive fuel and looses all power.


Background: Purchased car from auction in Melbourne. Collected with engine light on. OBD2 scan showing error relating to camshaft timing. Car was drivable (just) and decided to take a chance and make the trip to Adelaide. Every uphill part of the trip was a struggle, back through gears and slowing until just managing to the top. Pointless accelerating as boost just flew to max, turbo screamed and no gain in power.

Back home in Adelaide. Compression running at 80psi accross all 4. Dont completely trust my old comp tester but given low compression and ther OBD2 error scannned I decided the best bet was timing chain/tensioner replacement. Ordered a quality kit and timing tools from germany, fitted. Error gone but road test... same problem. Retested compression... no improvement.


Decided to take the head off and check it out. Massive carbon and gunk everywhere. No piston crown damage at all but 2 inlet valves noticably bent. Cleaned all carbon buildup, replaced all 16 valves, new head gasket and all the other stuff required, new oil etc. Compression tesed ... better, 180psi +/- 5psi accross all 4. No error codes. Road tested... GRRRR No improvement.

I'm very confident the engine internals are all spot on at this point so turned attention to charging system / Intake / Exhaust / Sensors / Actuators and this is where I hope someone here might have some thoughts.


Charging/Intake: Compression tested intake, two slight leaky points (perished O rings in intercooler piping) fixed. No improvement. Happy with turbo and intercooler, Gauge reading boost under load and OBD2 doctor app reading a corresponding pressure build in intake.


Exhaust: Worried that it could be a severely restricted exhaust I removed Downpipe (Cat) from Turbo. Very noisy lol but no improvement.


Sensors/Actuators: I noticed on dynamic data on OBD2 Doctor app that the short term fuel trim was often at -25% (maxed out) which could be telling computer to richen the mixture. Also noticed a strange air/fuel ratio reading of 2 (ridiculously high). Maybe the oxygen sensors (lambda probes) are somehow reporting a super lean condition I swapped them around (pre and post cat had same part numbers) but no improvement.


I dont trust the cheap ELM327 OBD2 interface or the android apps Ive been using so I've ordered a VAGCOM HEX V2 USB interface with VCDS software. Whilst waiting for this I thought Id ask around for help and try make contact with the previous owner.


Any thoughts????

Cheers, Kym


BTW, if anyone wants a lend of the timing tools etc, drop me a line, happy to help!!

[Greenvagride]

Camshaft position sensor, is a common fault of mark V variants. Can cause a heap of issues.

[voca]

Thanks... I'll check that closely.