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Discussion Starter · #1 ·
Hi Guys,
My AUM engined GTI has been fine since I bought it back in May but on Saturday it decided to throw me a check engine light. Happened whilst pulling into my driveway but was stopped when it came on with the engine idling.

Code scanned and comes back as a P0171 for Fuel System Bank 1 too lean. Common code on 1.8Ts as they a prone to vacuum leaks.

Fuel trims on the DTC freeze frame where -2% for STFT and 0% for LTFT. MAF Reading was 2.1g/s

Cleared the code and restarted engine to see if it would come back. Nothing.

Later that evening went driving for about an hour and a half, mixture of cruising and WOT in all gears, with my phone hooked up to my Bluetooth ODB reading looking at fuel trims, maf reading, Wideband O2 equivalence and boost. All looked normal. No check engine light.

Today whist sitting in traffic again the CEL comes back on, same code, idling, stopped in traffic.

DTC freeze frame was pretty much the same as the last time,

When I got home had a nose around the engine and couldn't hear any obvious vacuum leaks.

At idle, the Wideband O2 reads around 16:1, but at 2000,3000, and 4000 rpm reads between 14.5 to 14.9.

Anyone have any idea what's going on here?

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Discussion Starter · #2 ·
Turned out to be a massive holes in the hose from my PCV check valve to the intake manifold:
e6cf7e6fe20080032822e959f2afef9e.jpg


0ae23e05b1931b886ce053e482e00692.jpg


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Discussion Starter · #4 ·
It really is, somehow the car was still making boost as well. Probably over worked my turbo to shit running it like that nearly 6 months

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and this is the reason why it's best to replace the oem rubber pipes and hoses with Silicone versions... granted if you do it all in one go it's expensive but it eliminates things like this happening as they are made to withstand at least twice the pressure the oem pipes and hoses are capable of holding
 
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