Hey there mk6'ers I really need some help.
I have a 2012 mk6 GTI which Ive had for a year and have had zero problems up until now
Around a month ago my car lost a lot of torque, thinking that it was just the fuel I went through a couple tanks and ran some fuel cleaner through the system to try to help. I also replaced the fuel filter itself, yet none of this helped.
After dealing with this for quite some time I took it to a european specialist to find out what is really going on. With some time with the car, the mechanic there told me that there is a issue but he's not exactly sure what it is. Come to find out, the car that I bought is tuned with a tune I have no idea what is (They checked for giac and APR and it is neither) and there is an issue with the timing. In his words: the timing is too fast for what it should be but nothing is showing why. A possible fix in his words were either a reflash with the tune (but I'm unsure with what tune it has) or something mechanical possibly the catalytic converter being worn out. Asides from those two ideas he said that you could pretty much start replacing parts and never stop. The mechanic recommended me to keep driving the car just not at full throttle to hopefully reveal a code. There are no codes on the computer not even soft codes checked with a VAG com. I think this is a decent idea but I already put around 2k on the car with the same performance lack I do not believe that it has gotten any worse and definitely not any better for that matter.
I replaced spark plugs 6k ago along with a full service of the DSG. I always use 93 octane fuel and never kill the car. I'm really here to find an answer or possible ideas from people here that might have had the same issue as me. Thank you all very much for your time.
Thoughts that come to mind:
1.) OP did not specify what "timing" was referring to, some in the thread immediately jump to valve timing, but the other obvious answer is ignition timing. What the mechanic told you is too vague to use as information. Same goes for the catalytic converter, I cannot think of a causal link between a failed cat and reduced torque with no CEL. So far your mechanic's advice is suspect.
2.) What else changed when the car lost torque? Anything like an ECU update at the dealership, or even inadvertently putting the car into stock mode could have taken away the added torque that the tune gives.
3.) Did the torque reduction occur after you changed the spark plugs? What did you set the gap to? Is the torque reduction consistent or does it come and go? Did you properly torque the spark plugs when you installed them? They have a habit of loosening themselves which can cause blowby.
4.) Logs logs logs. Get a way to log boost, ignition timing, maf, etc. while you're driving the car. If the car is stage 1, you should expect something north of 14 psi, possibly even up to 18 or 20 psi depending on the tune. Stock boost levels are almost always less than 10 psi. If you can (with VAGCOM or OBDEleven or something more than just a scan tool), also monitor ignition timing correction factor, which will tell you if the car is getting spark knock. Also check N75 wastegate duty cycle.
5.) Boost leaks, check them. Diverter valve, PCV plate, etc. Almost all boost leaks should be accompanied by some kind of squealing noise though when under boost.
6.) Because you aren't getting any trouble codes or CELs, I'm almost certain the car somehow got back to a stock tune, probably inadvertently. If the car was tuned and not meeting requested boost due to N75 failure or boost leak, that would throw an underboost code. Same with repeated misfires, or many other things. I also highly doubt that it has anything to do with cam timing, because even 1 tooth off will cause the car to run like absolute shit and throw cam timing related trouble codes, and it will feel broken, not just down on torque.
