Engine Knocking - Can't Figure Out The Cause

[MeepLaw]

Hey all!

I've been having a consistent issue with my Mk6 GTI. 65k miles. It currently has a stratified stage one tune. During in town or lower RPM driving, my accessport is showing a consistent knocking where it'll sit at -3.75 for several minutes, with rare spikes over -5. Here's what I've tried so far -

• Different tunes. Even on a stage 0 map it'll still knock
• Switched out the intake for a cold air intake. No change
• Had a stock ignition coil go out, swapped to r8 coils, no change
• Different gas stations, 93 oct only, no change
• Different spark plugs, double checked gapping. No change
• Changed the oil, using Mobil 1 0W40. About 3k miles since oil change.
• Gas mileage seems fairly poor - even with calm driving I only got 24mpg with majority casual backroad driving, with my normal driving I average about 22mpg. Not sure if this is related or not.
• I've taken it to mechanics, who can't find anything wrong
• It's a 2014, so it shouldn't be affected by the timing chain issues (right?).

I'm at a loss at this point on what else it could be. Any help would be greatly appreciated

 

[Saabingti]

Maybe the PCV? Maybe the MAF?

 

[Grabbit]

Do you have any logs showing any knock? Have you done a de-carb on the car? If not, 65k miles is a lot to not have had this done. Might be worth borescoping through the spark plug holes to see if there is gunk on the intake valves. There are some pretty cheap chinese borescopes that hook up to your phone on Amazon that might be handy for this. Carbon also affects the injector nozzles if its really bad.

 

[MeepLaw]

UPDATE - took the car in for an inspection and parking brake issue. I just got it back, and now it was throwing a P0507. Completely uninstalled the tunes and took it to factory, now it’s throwing a p0300, p0301, p0302, and a p0304. Didn’t have any codes before I took it in.

No carbon cleaning has been done as far as I know, but I’ve only had the car since about 52k. The shop that just had my car insisted that there’s no way it has a buildup, since the mileage was “too low”. Shop was sketchy in other ways though, so I definitely don’t trust them

 

[BudgetPhoenix]

Sounds like a vac leak somewhere. Check your intake track and the pcv, and the breather hole on it to see if its sucking any air

 

[Joe_Mama]

Do you have any logs showing any knock?

Yeah you need to record some logs if you want any of us to really troubleshoot.

OP do you have any way to record logs?

There are some pretty cheap chinese borescopes that hook up to your phone on Amazon that might be handy for this.

This^^

I remember when you couldn't get one for under a few hundred. I bought a cheapo off amazon and it works great. Definitely recommend it

https://www.amazon.com/gp/product/B01MYTHWK4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[MeepLaw]

Sorry - one more update.
I’m not driving the car for now, if I do I’ll record some logs. Car is now throwing a p2279, along with p0300-p0304.
I’ll just try to limp it to a shop. I’ve checked under the hood, and nothing looks out of place. Double checked the connections on the intake, and looked around for anything that was obviously wrong, but no luck.

 

[AAnton]

"The shop that just had my car insisted that there’s no way it has a buildup, since the mileage was “too low”.

Agreed, that statement is BS. Car could have serious carbon buildup even at that mileage. Mine at 28,000 miles had pretty significant buildup.