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Timing chain tensioner failure?

icy604

Passed Driver's Ed
Hello everyone, I am in the process of diagnosing my currently broken mk6. Ill give you guys the back story. Any help or insight would be wonderful. So here goes...

I was driving my car the other day and felt a very strong hesitation when I went to accelerate at normal city driving speeds. I set off from a stop sign as you normally do, 1st gear, 2k rpms to 2nd gear. I went to give it a little bit of throttle maybe 20% in 2nd gear just to get up to speed because there was someone coming up behind me quite quickly. My car hesitated and became very sluggish and I immediately thought to myself *misfire*

I immediately see the check engine light flashing so I put the car in neutral and coast until I see a safe spot to pull over 5 seconds down the road. I shut the car off and I read the code on my obdeleven and it reads a misfire cylinder 4 code and a random/multiple misfire code. I clear the codes to see if the car starts... and it just cranks, no firing. I then swapped coil 4 and 3 to see if it would start and then the misfire would follow. The car just cranked again...

I always keep a set of ignition coils in my trunk so I swapped those in (slightly used oem bosch) for the genuine oem R8 coils (not knock offs) i had installed at the time. Same thing, just cranking, no firing. So I go back to the R8 coils and give it a bit of gas on while trying to start it and it fires up hesitantly.

It was idling like it had a misfire and the cel came back on so I shut it down to read the codes again. The current codes are misfire cylinder 2&4 as well as the random/multiple misfire code.

I had the car towed to my work (I work at a porsche dealership) and had a former VW technician of 20+ years briefly look at the problem. He had me attempt to start the car (just a few cranks to see if it sounded like it had compression). He said it sounded like it had compression. That's where we left things until tomorrow morning, we will be doing compression testing.

Important things to note:

-My car has an APR downpipe and their most recent 'stage 2' software, a K&N intake, southbend stage 2 clutch

-2k kms ago I installed a fresh fuel filter (6.6 bar revision), ngk bkr7eix plugs, and genuine oem R8 coils from DAP.

-my car has 111,000 kms on it and I do oil changes every 7k kms

I have 2 possibilities in my mind right now. I think the timing chain tensioner is done, or it is a fuelling issue.

Thank you in advance for your response :)
 

BudgetPhoenix

Autocross Newbie
I have heard of a stretched chain skipping a tooth and still run but i'd imagine you'd be seeing misfires in all cylinders. Who knows though without pulling timing cover to measure timing. Could also a fueling issue or even a simple fix like a vacuum leak.
 

icy604

Passed Driver's Ed
I have heard of a stretched chain skipping a tooth and still run but i'd imagine you'd be seeing misfires in all cylinders. Who knows though without pulling timing cover to measure timing. Could also a fueling issue or even a simple fix like a vacuum leak.
We will be looking into it tomorrow, if we're pulling the timing cover off I'm just going to end up doing the chain, tensioner and valve cover gasket at the same time.
 

icy604

Passed Driver's Ed
I have heard of a stretched chain skipping a tooth and still run but i'd imagine you'd be seeing misfires in all cylinders. Who knows though without pulling timing cover to measure timing. Could also a fueling issue or even a simple fix like a vacuum leak.
What kind of fuelling issue might it be? Hpfp?
 

Allchokedup

Autocross Champion
Sounds about what happened to mine. I was able to get it started and limped it down the road to buddies shop. Did the chain and didn't have any bent valves. However it created a slew of other issues and ended up having to replace the motor. I hope it works out better for you, maybe trade it in on a 911? :)
 

icy604

Passed Driver's Ed
Sounds about what happened to mine. I was able to get it started and limped it down the road to buddies shop. Did the chain and didn't have any bent valves. However it created a slew of other issues and ended up having to replace the motor. I hope it works out better for you, maybe trade it in on a 911? :)
What were the other issues?
 

Allchokedup

Autocross Champion
I cranked the car at work and the dash lit up like a Christmas tree. I did the chain and everything seemed to be good for a week or so. Then oil light came while driving home and car shut off. I checked oil it was good so I fired it up. I mean at this point if there's no oil pressure I figured its cooked anyway.
Needless to say there was no oil pressure and I had somehow sheared off the balance shaft mounting tab. Maybe the screen dropped and caused the issues. Either way it was a cluster.
Good news is if you own a socket set and some xzn's you can pull the motor and get a replacement for about $2500

Budget Phoenix helped me with my issues, dude is a wizard
 

icy604

Passed Driver's Ed
I cranked the car at work and the dash lit up like a Christmas tree. I did the chain and everything seemed to be good for a week or so. Then oil light came while driving home and car shut off. I checked oil it was good so I fired it up. I mean at this point if there's no oil pressure I figured its cooked anyway.
Needless to say there was no oil pressure and I had somehow sheared off the balance shaft mounting tab. Maybe the screen dropped and caused the issues. Either way it was a cluster.
Good news is if you own a socket set and some xzn's you can pull the motor and get a replacement for about $2500

Budget Phoenix helped me with my issues, dude is a wizard
And the initial issue that you experienced was similar to mine?
 

icy604

Passed Driver's Ed
https://www.golfmk6.com/forums/inde...chain-tensioner-failure-thread.240478/page-95
Yep, except I didn't have a scanner with me so I dont know what misfires I had.
I can say it's very likely its not your coil packs.
I wish you luck sir
UPDATE:

We did compression testing on all 4 cylinders today and they came back pretty good, 160psi on all four (give or take 5 psi) after 5-6 cranks.

We then tested the fuel pressure by pulling the feed line off of the hpfp and running it to a gauge. While we were cranking the car we weren't expecting much mess so the spark plug wells were left uncovered. We cranked the car and a geyser of fuel shot out of cylinder 4 (the initial misfiring cylinder when it broke down last week).

We used a borescope to check out the inside of cylinder 4 and it was literally flooded with fuel. Once it was evaporated we took another peek to find some very nasty carbon buildup on the top of the piston. Cylinder 1 looked quite nasty as well. (Thought there was no apparent flooding in cylinder 1)

My guess is that this injector has been acting up for a long time and I didn't have the sense to address it. When I would get a misfire i would just change plugs and coils and be done with it.

My lack of sense finally caught up with me lol. Needless to say 4 new injectors are on order along with the manifold and throttle body gaskets among other things.

My question is whether or not I should still be thinking about the tensioner as a concern at this point in time...
 

Allchokedup

Autocross Champion
yes, be thinking about the tensioner if its never been done.
Glad to hear you only have to replace some injectors! Let this be a lesson not to overlook necessity items. Clean the valves while you are in there
 

icy604

Passed Driver's Ed
yes, be thinking about the tensioner if its never been done.
Glad to hear you only have to replace some injectors! Let this be a lesson not to overlook necessity items. Clean the valves while you are in there
Yes we will be scraping the backs of the valves while we're in there, my work doesn't have a walnut blaster. A concern of mine was pistons 1 and 4 had a lot of carbon on the faces of the pistons around the edges (likely from the injectors being faulty). Will this eventually burn off once the car is running properly again?
 

Allchokedup

Autocross Champion
Yes we will be scraping the backs of the valves while we're in there, my work doesn't have a walnut blaster. A concern of mine was pistons 1 and 4 had a lot of carbon on the faces of the pistons around the edges (likely from the injectors being faulty). Will this eventually burn off once the car is running properly again?
No, that is an issue with direct injection. Has to be cleaned manually, unless you have meth injection to spray on the back side of the valves
 

icy604

Passed Driver's Ed
No, that is an issue with direct injection. Has to be cleaned manually, unless you have meth injection to spray on the back side of the valves
I was referring to the carbon on the faces of the pistons, i am aware of the whole direct injection and gunky intake valve situation. Ill see if I can get a photo of it off of the borescope tomorrow and share it on this thread.
 
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