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Engine shudder and throwing codes.

Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Having engine shudder issues. Replaced all spark plugs and coil packs. Already had them sitting and waiting. Cylinder 1 looks to have carbon build up. Cylinder 2 buildup and scoring. Cylinder 3 was the one that had the missing spark plug tip and scoring. Cylinder 4 scoring, carbon, and what seemed to be oil. Something wet. I honestly have no idea, and would appreciate some feedback.

The engine shudder stopped after replacing coil packs and plugs.

15 Mk7 GTI, 67k miles, 57k miles tuned Unitronic stage 2 ECU/TCU.
 

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Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Your plugs look like shit. Were they torqued down properly? Looks like you had blowby past the threads on 3/4.
I'm gonna be honest here. I did it 10k or so miles ago. That being said, I didnt have a torque wrench at the time.

When pulling 1, 2 and 3, they were loose.

On the way home after I picked the car up from the body shop, it went into limp mode. No shudder, but lost power and then picked back up again. Any thoughts, as to why this keeps happening and plug 3 missing the tip? What does this mean? I'll have to wait until Monday to get it towed to the shop as I'm not sure what else to do with it.
 

Diggs24

Autocross Champion
Location
de plains! de plains!
Car(s)
2015 GTI; 2003 Saab
You have a lot of detonation on your pistons, likely from the loose plugs. Plug 3 probably gave up and the tip bounced around in there. The tip might have damaged a valve.

Also, I'm confused on what's happening. You replaced plugs and all 4 coils (yes?) and now it is doing _______________.
 

Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
You have a lot of detonation on your pistons, likely from the loose plugs. Plug 3 probably gave up and the tip bounced around in there. The tip might have damaged a valve.

Also, I'm confused on what's happening. You replaced plugs and all 4 coils (yes?) and now it is doing _______________.
Replaced all 4 plugs with the RS7, and 4 coil packs the RS3.

It was driving fine. Then after 2 miles it went into limp mode and lost power. It then picked back up and seemed, OK. It makes me hesitant to drive it. The power is coming in and coming out. But, it is not throwing a CEL. Im honestly baffled, it is beyond my limit of understanding. You guys seem to know your stuff.
 

Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Just went on a mile test drive. This is what was going on under load. Any ideas? Cylinder 3 was the one missing the tip of the spark plug, but cylinder 2 was having crazy misfires. Happened as soon as I went into sport mode and slightly tapped on the throttle.
 

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Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Unhook your purge valve connector. He touches it at 3mins.

I opened up cylinder 2 again. Do you think the object to the left in the cylinder is the tip of the spark plug? I attempted to move the car in my driveway, it starts and instantly turns off now.
 

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Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Time for a tow.
It is booked in for Monday at 9 am to be towed to a VW specialist. More to come. I'll keep the thread updated. I suppose not too much information through the weekend. Maybe some negligence and inexperience led to the fault. More to come for sure.
 

Ecapskcab

Ready to race!
Location
UK
Car(s)
15 Mk7 GTI
Just curious but what did you torque the new plugs to?
Initially they were hand tight but afterwards they were torqued to 30nm. Once I torqued them down I started having issues with the car not wanting to idle. At that point I booked a tow because I'm out of ideas as to how I can manually diagnose my car. 🤷‍♂️. I have the weekend, before the tow. I'm open to ideas.

EDIT. Spoke with a local mechanic from the pictures, stated the piston broke apart. Suggested a used engine for a swap. Said it would be a lot cheaper than trying to fix mine.

Dilemma: It is a US model car with engine code CXCB. Can I swap a UK engine for say a Golf R (CJXC)? When doing so, how will it affect ECU and what should be looked out for?
 
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