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'07 K04 GTI Misfires

snobrdrdan

former GTI owner
That's deceptive as hell. Even the questions down below state the brand is "Original Equipment." Will pick up the Genuine VW/Audi coils and see what happens. I swear if this is the root of my problem after all this... ?

Will add, I had red caps on the car before going K04 and I believe they were the same part as what I'm running now, but I guess those are okay to use on Stage 1/2 applications.

I've seen people have issues with those ones....I still swear by the OEM ones
Let us know what happens
 

BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
They should be here today. If it's not raining after work I'll throw them in the car. Had I known they were not OEM I would not have gotten them.
 

BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
New coils installed. Revision G made by Eldor. Immediately felt the car idles better and is smoother on power delivery. Misfires in the upper RPMs still happening. Haven't had a chance to get on the highway with her yet. Will try to go for a ride early in the AM.

Wondering if I need new spark plugs after running them so long like this. If not that...what else?
 

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snobrdrdan

former GTI owner
Those are the latest/greatest revision...glad to hear they did something though.
I'm not sure about the misfires (never went K04), but I'm sure it wouldn't hurt to try new plugs too since they're not that expensive and make sure they're gapped right too

Are you due for a carbon cleaning? FSI still needed that to be done, btw

Similar (old) thread with some tips:
https://www.golfmk6.com/forums/inde...ed-at-026-which-plugs-gaps-do-you-use.290791/
 

BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
Plugs replaced and gapped to .028 per Unitronic. Issues still present. The misfires are a bit more aggressive with the new plugs. Guessing the car just needs time to get used to them. The old plugs looked pretty decent. Nice golden brown burn color on all four.

Carbon cleaning was done at or around 90-95k miles so I'm probably due again.
 

BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
Switched back to the old plugs. May have damaged one when gapping. Ordered a new set and a tool that will allow me to dial in the gap safely/accurately. Will update again once that's done.
 

BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
Alright new plugs gapped with the tool and installed. Car runs even smoother/peppier than before, but the problem still exists. Means I can rule out ignition unless something is up with the wiring harness. Any other ideas?
 
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BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
Just another update. Rotated coil in cylinder 1 to cylinder 2 and spark plug from cylinder 1 to cylinder 3. Misfires still on cylinder 1. Looking into replacing that injector.
 

RacerFreddy

Passed Driver's Ed
Location
Pennsylvania
Car(s)
Mk5 GTI
Don't want to hijack the thread, but I have anecdotal woes of K04, and would like to add in and talk it through.

I have similar issues/quirks to this day. Although I'm APR and I want to blame the tune mostly, looking into Unitronic myself. I had a hard misfire "wall", like yours, replaced Cyl. 1's S3 injector recently and it fixed the up top RPM cut. However, now it misfires every once and a while at idle after it drops into normal RPM on cold starts, once it starts warming up. (EDIT* I do not have a RFD) After driving I come to an idle and it misfires more often after its fully up to temp. Same cylinder I just changed the injector on, tried plugs and swapping coils and still no luck, tried sourcing vacuum leaks, tried a new MAF and intake setup and nothing changes. Cylinder still shows signs on the plug of running lean, and fuel trims were unusually high.

VagCom is great, but logs have always looked normal, aside from those fuel trims, I need to check them again, but it hasn't told me anything aside from Cylinder 1 misfire as of replacing that injector and having a poor idle. Hell even AFR, vacuum, and RPM act steadily enough at idle.

For OP, I would do the injector and take a close look at any potential carbon build up in there. I need to do the same, but I really want to try Unitronic and replace some other maintenance items, and throw a catch can on just to see if that helps.

General questioning, does a poorly functioning rail sensor, or lower pressure relief valve, have any possibility of misfiring and leaning out one cylinder?
I would believe that would cause fuel starvation across the board. That would likely show up in VagCom logging as well. What else could lean out one cylinder? Even mechanically, valve seals, springs? Surely not at idle.

I want to say fueling is still my issue, but I understand an injector failing to produce at high RPM like mine originally. To be able to keep up under high load but not at idle seems illogical. I would guess to much air is getting in, but I don't have signs of a vacuum leak, and again would expect issues across multiple cylinders.

There's so much that can mess with the K04 tunes it's not even funny.
Sorry for rambling, but IMO more talk is better in the forums.

After rechecking fuel trims, idle adaptation sits richer, at -2.3%, while partial sits a lot leaner at 11.8%, what could cause such a wide swing between the two. My gauge always shows rich under boost, dips down into the 10s and 11s in AFR under 19-20 psi. I don't get it, it points to vacuum leaks but I can't source any. Resetting fuel trims makes it idle like garbage at first, then the live adaptation fluctuates between about -3% to positive 5%, looping over and over. Idle smooths out but I get a Cylinder 1 misfire and a puttering backfire every time it does, I just changed that injector, could it be a seal issue?
 
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BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
As long as the seals/clips were new with the replacement injector I would imagine it's fine. I too get misfires on random cylinders when just cruising around town, but it's normally just 1 on a random cylinder or two. When I hit the wall it's all on cylinder 1 now. My plan is to swap all four injectors with genuine VW Golf R injectors (same part number as S3 06F906036F) as the ones on the car now are Bosch which I got from eBay. Not too thrilled about shelling out the cash for another set, but it will rule them out. Probably should've gotten genuine injectors to begin with. Plus if there's no change I can sell the ones on the car now. I'll take the opportunity to get the valves cleaned while the manifold is off as it's been about 30k miles since it was last done.

I also got a response from Unitronic who said, based on the log data I shared on the first post, the motor goes terribly lean after 5500rpm, but all data values except for lambda look fine. They also said I'm pulling a dangerous amount of timing which could indicate the quality of fuel is really poor or there's an issue in the combustion chamber causing the knock correction to be so high.
  • On your rail sensor question, if you're not running the latest revision I would look into doing so (06J906051D).
  • As for FPRV, I am running a 145BAR valve from HPFP Upgrade and the logs only showed one or two spots where pressure exceeded 130BAR, but Unitronic did say overfueling the system could create the scenario I am experiencing if not a faulty injector or bad gas. Your logic seems sound and you'd likely experience a fuel cut instead of a misfire which feels more like a bucking of the car. Got that once with a full car of people when I accelerated from a stop at a light. Replacing the LPFP and control module fixed that.
  • On your current misfire issue, it does seem odd, but sounds like the injectors are working well and perhaps something else is up. Does APR require you to gap plugs to .028 like Unitronic? What coilpacks are you running? Would also check your low pressure sensor on the HPFP to make sure it's the latest revision too (06E906051K).
Since I've ruled out coils and plugs properly this time the injector(s) would be a good next step; albeit an expensive one. Aside from that, weak valve springs or possibly a vacuum leak could be a culprit, but I sit right around 19-20Hg when idling which seems decent to me. Would rather do the injectors before looking into valve springs.

Despite ongoing issues, the car has tons of power before 5500RPM. Super smooth and an absolute blast. Especially with the DSG tune on it. I've just learned to take it easy so I don't hit the "wall" I've described. It's fast enough for around town doing just that, but I'd like to see what she's really capable of. Plus, the misfires across all four cylinders on cold starts is getting old and is even worse now with the cold weather. With the flaps installed it was not so bad.
 
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BurgerGuy

Drag Race Newbie
Location
Charlotte
Car(s)
'07 K04 GTI
An update. Turns out the spark plugs I was running (BKR8EIX) are two heat ranges colder than stock, but the tune calls for one step colder (BKR7EIX). Swapped to those which helped a bit, but OEM Golf R injectors fixed everything else. She's running like a top now.
 
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