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It all started with 'cylinder 2 misfire' and has been a slippery slope since.

fattypros

New member
Location
San Diego, CA
Car(s)
2017 GTI
Hi all,

I am recreating this post on it's own thread since I've had confirmation it's not just a spark plug issue.

I am the sole owner of a 2017 GTI Sport M6 with Performance Package that is about to hit 70K miles, a lot of highway mileage it is stock with the exception of the clutch that failed which was replaced with a stage 1 (forget the brand, although it lacks springs and is noisy as all get out) and the brakes and rotors because it was cheaper than OEM.

Maintenance intervals have been followed by taking the car to the stealership for all service, it all being performed with the exception of air filters and brakes/rotors as mentioned above, I made those changes myself. All prompts to 'check oil level' and 'add oil' have been followed, oil changes occurring regularly.

This car is a little under year from being paid off, 4500 remains on the loan, I was really looking forward to a lack of car payment next year.

I've only ever had one instance of a steady CEL with the 'cylinder 2 misfire' code happen almost 5 months back, but the engine didn't feel like it was struggling or seem out of whack, so I cleared the code with a 20 dollar Amazon code reader and waited for it to return. I probably should have inspected cylinders then, but hind sight is always 20/20!

It didn't seem to, so I thought things were all good.

Fast forward to a few weeks ago, my car starts shuddering when I put the accelerator down more than slightly in the RPM range of 1500-3000. The work around was either feather the pedal slightly, or upshift to get to the higher RPMs.

I couldn't get another CEL so I wasn't sure where to go, until 2 nights ago. I was traveling for work and finally got a flashing CEL briefly when giving the accelerator a heavier push on the highway. It disappeared but I was looking forward to getting back home to use my cheap scanner to figure it out.

On the way back home from my work trip, I had to upshift and give it the beans on the highway, and the car was not happy, a steady EPC light (does it ever flash?) and CEL flashing, but not stopping, I went back to cruising and feathering the accelerator, and the CEL became a steady light.

Before continuing on, I stopped at Autozone and used their code reader, and what greets me? the 'Cylinder 2 Misfire' code returns! (I forgot the number, sorry).

So I carefully continue, eventually making it home and parking for the night.

The next day, I get to work removing the coils and plugs, starting with cylinder 2 and am greeted with this:
tempImageBMAF6q.jpg


All four plugs (1-4) :
tempImagegM4foC.jpg


Cylinders as follows, I am awaiting a 24mm socket to come tomorrow to manually turn the engine to get a better look, although it's likely a moot point now.

1 piston crown and side wall
cyl 1 face and wall screen cap.png


Cylinder 2 piston and side
cyl 2 screen cap.png

cyl 2 wall screen cap.png

Cylinder 3 piston crown (no side pic, looks similar to others.
cyl 3 screen cap.png

Cylinder 4 piston crown and side
cyl 4 screen cap.png

cyl 4 wall screen cap.png


I ran a compression test and the results were as follows:

1: 175 psi
2-4: 180 psi

So cylinders 1 and 4 look pretty good, 2 and 3 look like the bottom of the oven when food falls on it, but the cylinder walls look similar, once I get that socket, I will cycle each piston again and take look at the entire wall.

I replaced all 4 plugs with OEM, put the coils back in swapping 1 and 2, started it up, and everything seems fine. I took it out to the highway, recreating the conditions of more than slight acceleration in that low RPM range, no bucking, no CEL, everything seemed good.

I am still very concerned about where the electrode went, but it's not in the cylinders. I do still plan to remove the intake manifold and move forward with the walnut blasting. I will be sure to check it fully and document that process too.

My luck with cars is never that good, hence why I have decided not to purposely modify beyond stock, no tuning for me. I modified a wrangler with 20k worth of stuff that never got me anything back, so I am content with what I have here on the GTI. But I feel like the broken electrode was product of another issue and not the cause.

When I pull the manifold for blasting, I am thinking about pulling the injectors to scrub the face, but cylinder 2 looked the worst (I can only attach 10 pics, so the injectors are the odd pics out)

The things I don't understand include the following:

-IF the missing electrode was the culprit, why did the engine seem fine in so many other instances besides the slight acceleration? I would think the CEL would be flashing all the time and I'd have more codes like 'hide cylinder'
-WHAT the HECK is going on with the differences in piston face appearance between cylinders 1,4 and cylinders 2,3? I would probably need to remove the head to get in and clear that stuff out, if it's even worth it.

Diggs24 provided the following assessment:

Those plugs look horrific. As do the pistons on 2&3.

Bad: You either have such a horrific leak at the cam cradle that a massive amount of oil is making it into the cylinders that the spark plug could no longer fire consistently.

Worse: The piston rings in 2/3 are toast and the engine needs a rebuild.

Neither are a cheap fix. You are way past carbon cleaning or injector replacement solving anything.

Daks got straight to the point:

Get rid of the car. That thing is jacked as shit. Trade it in, do something. I'd get rid of it.

Scrllock provided the following:

if you can't afford to trade it in you definitely can't afford to not fix it. at the very least clean all that gunk out.
my guess, injector #2 is going, was running lean and melted the strap.
the car has 70k on it right? was anything maintained prior to this? injectors, plugs, coilpacks?

And Acadia18 added this:

My thoughts exactly. That is not a healthy engine, and in my far from expert opinion, looks like a ticking time bomb to a very expensive repair.

It seems like you have a good plan in place though. As long as you're not just sticking your fingers in your ears going "blah blah blah it's running fine for now!" and ignoring that there's a deeper issue, hopefully you can prevent that from happening.

AND THAT's the summary from the thread I hijacked before creating this one.

I am not sure where I am going to go next with this besides do more research, as I am working out of my garage and lack most of the tools to do an engine tear down.

My wife works from home so I could use her car in the interim although I know she wouldn't be thrilled about it.

I will probably get in touch with the local shop to see what they would charge, I'm certain its more than the remaining loan amount on the car.

The frustrating part is trying to do everything right, and still getting bit in the ass in the end. I do need to top off on oil quite frequently, should have brought it up while under warranty I guess.

I hope your car adventures are going better than mine!

Whatever the next steps I take are, I will catalog them here. Thanks again to @Diggs24, @Daks, @scrllock, and @Acadia18 for the feedback so far.

If you took the time to look at all this, I hope something helped you. If you have questions, please let me know and I'll try to answer them to the best of my limited knowledge.
 

Acadia18

Autocross Champion
Location
The Greater Boston Metropolitan Area
Car(s)
2019 Golf R
Bad: You either have such a horrific leak at the cam cradle that a massive amount of oil is making it into the cylinders that the spark plug could no longer fire consistently.

Worse: The piston rings in 2/3 are toast and the engine needs a rebuild.

Neither are a cheap fix. You are way past carbon cleaning or injector replacement solving anything.

If the piston rings were toast, wouldn't those cylinders not hold commission?
 

fattypros

New member
Location
San Diego, CA
Car(s)
2017 GTI
That crater appearance on the pistons is cooked oil.
Hence the food spilled on the bottom of the oven appearance I take it!
A video of #2 where we can see the cylinder walls all the way around would be beneficial. Vertical lines are bad news.
Once I get this socket and can cycle cylinder 2 to the bottom, I will go back in and video the full length of the cylinder and all others. I might have a view of what I could get so far....
 

fattypros

New member
Location
San Diego, CA
Car(s)
2017 GTI
So hopefully my issue is resolved.

Since I was expecting engine disassembly for repair, I contacted a local shop, they performed a diagnostic with a much better scan tool than my 20 dollar Amazon special finding additional codes which lead to indicating the oil separator had failed, along with low voltage for the alternator, and high pressure fuel pump issues. Additionally, they said a carbon cleaning was needed and most likely going to help with the misfires.

The price to address these issues wasn't catastrophic (1800 after military discount) and the work/parts were backed for 2 years/24k, so I gave them the go ahead to move forward. I asked for pictures of the valves before and after which are as shown (apologies for poor quality, gotta love a phone taking a picture of a screen!):
tempImagekLr2CF.jpg

tempImagenyygL5.jpg

tempImageXRTL8c.jpg

tempImageJC0SjH.jpg


Driving it feels a lot better, I plan to set a reminder to check the plugs and cylinders in 1000 miles as well as continue to monitor oil leaks and usage.

When I looked at my Amazon history, I purchased the cheap code reader back in February, so who knows when these other items failed? But I have much better peace of mind that other areas were addressed and hopefully no other big issues crop up.

The shop I received service from offers free diagnostics, I was going to get a better code reader, but since I have them as a resource, I am kind of on the fence.

I will provide further updates when I check the car in the future.

Thanks to everyone for their help and advice, if there are any further questions please let me know and I will try to answer them!
 

Acadia18

Autocross Champion
Location
The Greater Boston Metropolitan Area
Car(s)
2019 Golf R
So what did they do? Just replace the PCV and do a carbon cleaning? Was nothing done to address the two pistons looking like the bottom of an oven?
 

fattypros

New member
Location
San Diego, CA
Car(s)
2017 GTI
So what did they do? Just replace the PCV and do a carbon cleaning? Was nothing done to address the two pistons looking like the bottom of an oven?
So what did they do? Just replace the PCV and do a carbon cleaning? Was nothing done to address the two pistons looking like the bottom of an oven?
They performed a fuel service cleaning, comprised of fuel system cleaner, air intake system cleaner and fuel injection system cleaner.

I should have asked for the results of that in the cylinders too, I’ll have to take a look.
 
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