Slight hesitation/miss but only at light rpm’s?

[CTMK6GTI]

Hey guys, got a little bit of puzzler I was hoping to get a little help with. First off, my car is a ‘14 MK6 GTI 2.0T/DSG w/107k, basic stage 2 car (CAI, catted Downpipe, cat-back, stratified tuned). It’s got recent NGK plugs per stratified for their stage 2 tune, gapped to .028, has a recent PCV valve, DSG fluid done at 85k. Turbo and intake manifold both replaced at 45k under warranty when both failed within a week of each other, otherwise a zero issue car, and every other mechanical part is still original.

Fast forward to now, I’m experiencing a strange issue. I’ve noticed that lately, especially as it’s been much colder here, and usually more noticeable while the engine is cold before fully up to temp, that I’ve been getting slight hesitation/missing/bucking while driving around under light throttle, usually like sub-2k rpm’s. Tonight it also started doing it at highway speeds as well, sub-3k rpm’s, but again, only under light throttle such as maintaining speed, etc. When you get on it, or drive in S mode, keeping the rpm’s in a higher range, this issue is unnoticed. When it does happen, there are no codes, no EPC lights, and it’s honestly not dramatic but enough so I can feel it in my seat, and even my gf can notice it in the passenger seat. My first thought was that at 107k, I’ve actually never had a carbon cleaning done; mind you this car is driven quite hard periodically and I do try to go out of my way to give the valves a good self cleaning, but nevertheless, I’ve never had a proper, true carbon cleaning performed yet. Since this hesitation has began, I’ve since reached out to a buddy who works for VW that’s gonna try to get this done for me in a near Saturday for $350, I’ve just gotta get the car up 1.5hrs to him lol. However, I’m not truly convinced that this is all just coming from carbon buildup, but maybe I’m wrong, and that’s why I wanted to ask here first. I’ve read about numerous similar issues, a lot of them in regards to dirty/failing TBs, failing LPFP, dirty/bad MAF sensor, intake manifold runner flap failure, among other things, but so many threads don’t conclude what they finally found to be their fix, thus I don’t have many solid references. I also don’t have vagcom, however I do have a decent actron scanner that can monitor many PIDs and trims live, as well as a Cobb Accessport, that can also monitor and log a lot of info. I’ve also thought about reaching out to Alex at Stratified to see if they have any suggestions or recommend me refreshing my tune as I’ve had this file installed for over 60k miles now. If you guys have any suggestions, or could recommend some troubleshooting processes, I’m definitely all ears, and I’m pretty capable of performing most diagnostics and can report back findings as needed. I’ll also be sure to update my thread with my personal solution as well once I get this resolved; this is my only daily and I do intend to get this resolved and running perfectly as usual again. Thanks in advance for any help and suggestions!

Derek

 

[Joe_Mama]

carbon build up

/close thread

 

[AM407]

Yup. My first thought as well, just from reading the title.

Don’t overcomplicate this from the start, just do the maintenance (I.e. carbon cleaning.) Re-evaluate afterwards if you need to (but you probably won’t.)

 

[CTMK6GTI]

carbon build up

/close thread

Yup. My first thought as well, just from reading the title.

Don’t overcomplicate this from the start, just do the maintenance (I.e. carbon cleaning.) Re-evaluate afterwards if you need to (but you probably won’t.)

Fair enough, thanks fellas. Now let me ask you this regarding the carbon cleaning; is walnut blasting THAT much better and more efficient than just manually scraping and cleaning with chemicals? My reason being is that my buddy who works for VW has access to the media blasting, however he’s about an hour and half from me, and between the distance and availability, we won’t be able to meet up until probably earlier February right now. However, there’s an Indy who specializes in euro vehicles just the next town over who is super convenient, however he doesn’t have any blast equipment and does them manually by hand, and I could get in to him whenever, and certainly much sooner. Do you guys recommend I hold out to have the walnut blasting done, or is a manual cleaning just as effective, and just go get it done?

Then there’s the other, dirtier method; someone suggested I just unplug the manifold flap sensor on my intake manifold until it throws the p2015 code, then plug it back in, take it to the dealer for a warranty replacement while it’s still under the emissions warranty, and then just pay the extra to have my dealership do the walnut blasting while they’re in there… does this also sound like a possible feasible method? This was actually suggested by someone to them from their VW dealer, which they did successfully. Plus, I wouldn’t mind having my manifold replaced once more under warranty before the warranty runs out.

Thanks again

 

[AM407]

I did the cleaning myself using dental picks and scrapers and solvent. It worked well, but took me forever and gave me a nasty headache.

If someone’s getting paid by the hour, I can see them doing a better job with the walnut blasting. But it’s possible to do a good job with either method.

No comment on the manifold scam.

 

[This is Ryans face]

Could be intake manifold. I only say this because my engine has less than 10k miles on it and I get this sometimes when feathering the throttle from a stop and the driver in front of me takes their sweet ass time getting up to speed. I finally popped the 2015 code, last week, but it has since gone away and so has the bucking sensation and they haven't returned just yet. I'm also thinking that since we're both DSG, it could be the the slow/sloppy engagement of the clutch packs due to an aged or failing mech unit. Unfortunately, like all previous gens with the DSG, the solenoids in the unit get dirty with metal shavings and other gunk, and eventually start feeling like your first day as a school bus driver with clunkier shifting. Resets via VCDS help, but not for long. You can try this option first since it'll cost nothing or at least very little, then check flapper motor attenuation via measuring blocks (sorry, I forget which one) for abnormalities, and if there's still no change, pull the manifold and get scrubbing.

FWIW, I fully agree that if you're rolling on an engine with 100k+ miles without having done a carbon clean up, you should elect to do it regardless of if it remedies your issue fully.