FSI Cylinder 3 Misfire above 5k RPM

Hey all,

New Dubber here, bought a 2008 FSI in manual a few months ago. Love it, minus the maintenance costs I've had to throw into it. :help:

Started with misfires that I've been dealing with since day 1...driving it home, I got a flashing CEL going uphill WOT in 2nd gear. Didn't have a scanner at that point, so I replaced all of the spark plugs and threw in R8 coils. Didn't run into the issue again until a few weeks later in a similar scenario. Scanned it that time and it threw a Cylinder 3 misfire code. Checked the plug gaps and they were all fine (0.032) and swapped the coils in 3 and 4. All good until a few weeks later I got another one...this time I was slowly accelerating in 1st gear (not in boost) and went over 5000 rpm which triggered a flashing CEL. Scanned again, and yet another Cylinder 3 code.

Since these are new plugs and coils, my only guess would be the injector...or worse, bad compression in #3? The previous owner supposedly did their own carbon clean just before I bought it. Relevant mods:

-APR Stage 1 (Supposedly...only peaking 12psi, but it revs past 4k in neutral)
-APR Carbiono intake
-R8 coils as mentioned

All else is stock. Checking my DV soon to address the seemingly low boost, no PCV symptoms yet. Cam follower was replaced about 8k ago.

Any suggestions? Probably the injector, maybe the coil connector? Curious on your thoughts since it only seems to happen above 5000 rpm. Thanks

My first though was plugs/gap but those sound to be ok. I would verify that a carbon cleaning was actually done, either by borescoping through the throttle body or pulling the manifold.

If it is APR tuned, you can try switching programs from stock to others with your cruise control stalk: https://www.goapr.com/support/dpp_emcs_instructions.pdf

Come to think of it the previous owner mentioned "valve cleaning," so it could be that the valves were done but not the injectors or manifold. I unfortunately don't have the tools or garage space to rip the manifold off myself, and I'd really rather not spend the labour costs at a shop until I absolutely need to. Would running some cleaning additives in the fuel help?

Thanks, was looking into the mode switch soon.

cygnusx1 said:

Come to think of it the previous owner mentioned "valve cleaning," so it could be that the valves were done but not the injectors or manifold. I unfortunately don't have the tools or garage space to rip the manifold off myself, and I'd really rather not spend the labour costs at a shop until I absolutely need to. Would running some cleaning additives in the fuel help?

Thanks, was looking into the mode switch soon.

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cleaning additives wont clean the manifold or valves as the injector is in the cylinder.

eurocars said:

cleaning additives wont clean the manifold or valves as the injector is in the cylinder.

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Yes, I know. Assuming the valves had already been cleaned, I'm wondering if running additives in the fuel (and thus through injectors) would help out much, if anyone else has had much success with these.

Could be also a bad lubrication of cylinder 3 cams/journals leading to wear and bad action of the valves (worst case scenario along with low compression)

vwengineer said:

Could be also a bad lubrication of cylinder 3 cams/journals leading to wear and bad action of the valves (worst case scenario along with low compression)

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Yikes! Hope not. At only 160k km, that sounds too early for that kind of wear. Fingers crossed...

Is the spark plugs black or white?

That will tell you a lot. Also I'd like to see fuel and air/fuel ratio logs. Cheap $25 Bluetooth obd2 scanner can do this (what I use)

My car is doing the same thing and I've done the same maintenance as yourself. I have a 2006 Gti and I love it but I don't want the car to break me lol.

Him Downstairs said:

My car is doing the same thing and I've done the same maintenance as yourself. I have a 2006 Gti and I love it but I don't want the car to break me lol.

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Any luck?


I haven't yet found the cause to mine, but am able to reproduce the problem every time I go over about ~5200 rpm, usually with very little throttle and in 1st or 2nd gear (scared to do a WOT run to redline). Been waiting on an OBDeleven to come in from Europe to run some logs. I've noticed "pulsating" boost/acceleration in 3rd and 4th under about 60% throttle.

Confirmed to be on stage 1 after using the mode switch. Also looking at doing a fuel filter switch before winter as cold weather cranking seems to stutter a bit sometimes.

She rips well, but I'd love to be able to take full advantage of the rev range!

If you have torx bits, you can remove the intake temperature sensor on the manifold and get you a cheap boroscope that you connect to your phone. Just search Amazon for a "cell phone boroscope". Since its cylinder 3, it should be close to directly in line within that sensor hole.

I think I have somehow solved my issue, in the weirdest way possible. Replaced my super old and dirty K&N drop-in filter with a new OEM air filter, did a little bit of cleaning of the air box/engine cover....no more misfires! Or at least, none that set the CEL off...I can pull to redline without a flash.

My best guess was the filter was so clogged (wasn't horrible, but definitely not clean) that it restricted airflow such that it would cause a rich enough condition to miss at high rpm. I still have may suspicions about injectors, but for now, I'm happy :thumbsup:

Glad to hear things worked out in the end. Dirty filter and MAF can result in a missfires.

Unfortunate update, the filter seemed to help but not solve the misfire, it will still miss at very high loads over 5k rpm (usually wot). I haven't had time to run a log but the pulsing power that I've been dealing with makes me thing it's a fuel issue. Hoping to change over my fuel filter once I've got time, if not, the sensor on the hpfp (the last time I got a vcds printout, I had a P1093 code). HOPING it's not cam wear, the follower looked fine last time I replaced it. It seemed to miss less in the colder winter air, so maybe I'll have a look at cleaning the MAF too.

cygnusx1 said:

Unfortunate update, the filter seemed to help but not solve the misfire, it will still miss at very high loads over 5k rpm (usually wot). I haven't had time to run a log but the pulsing power that I've been dealing with makes me thing it's a fuel issue. Hoping to change over my fuel filter once I've got time, if not, the sensor on the hpfp (the last time I got a vcds printout, I had a P1093 code). HOPING it's not cam wear, the follower looked fine last time I replaced it. It seemed to miss less in the colder winter air, so maybe I'll have a look at cleaning the MAF too.

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I had a similar situation too, replaced all the necessary parts that u think was the issue but no. Took me a month trying to solve it. Had a k&n open filter too. Lastly I diy decarboning via the IAT sensor into the manifold and used amsoil power foam. Used up the whole can. Once the whole process was done surprise surprise misfires never came bk.
Point is, thick carbon buildups was restricting the valves etc to operate properly. I kept up using amsoil PI additive to clean the fuel system and chamber. Not on valves due to direct injection engine (fsi)
This was 2 years ago and it has been flawless til now.
Ps: i swear by amsoil.



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