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Author Topic: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three  (Read 237 times)

Offline Birty_

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Evening all,

Joined the group as I always search on here when I've got an issue and has been pretty awesome in the past.

So story time.... Sold my M2 Competition and decided to run around in my partner's MK5 ED30 along with modding it etc.

It's stage 1 R-tech, and was walnut blasted along with the injector cleaning around 2 years ago. They commented on the fact the injectors were not in a great state.

I've always had an issue with misfires on cylinder three, I was getting oil on the plug.  This was sorted with a fresh set of coils and plugs. Went back to R-tech for a health check and they changed the head gasket.

Car was running good, but the misfire would occasionally come back. Quick clean of the plug would sort it. Assumed the gasket just hadn't seated properly.

Fast forward today, decided to fit an RCD 330 and upgraded the canbus to 1K0-907-530-P as I didn't want any battery drain. Coded with VCDS and no real problem.

Turned the car on, misfiring on idle which is very lumpy. Came back as multiple misfire & cylinder three, swapped the sparks and coils and misfire remained in cylinder three. The plugs and R8 coils (AKS genuine) are approx. 6 months old. Plug in cylinder three was quite oily and is definitely the worst.

Thinking the worst, I got a compression test done -

1 - 170
2 - 185
3 - 180
4 - 180

Guys at the garage local to me suggested it may be a wiring fault or an ECU fault. They thought of the wiring harness to the coils. Just seems pretty random after the canbus was upgraded I have an electrical fault.

Anyone have any ideas? I'm no mechanic and would have no idea how to diagnose the above.

Appologies for the long windedness, and I appreciate any help.

Offline Pudding

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #1 on: November 18, 2021, 07:22:38 pm »
Sure it’s oil on the plug and not just fuel from all the misfires?

Sounds like you need a set of injectors in the first instance. No.3 usually goes first for some bizarre reason.  A bad injector or a mechanical fault are the only two causes of persistent misfires. Coils and plugs rarely fail to that extent.


2007 ED30 | 2009 TDI 140

Offline Birty_

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #2 on: November 18, 2021, 07:39:40 pm »
Thanks for the response.

I'm pretty sure, but I'm going to check again tomorrow. I'll stick some new plugs in just in-case.

Guys at the garage seemed to think the injectors were OK, but they didn't pull the inlet so I guess they can't be certain.

Just seems odd it was the moment after upgrading the canbus, but I can't see why that would cause any issues. May revet to the old canbus for a peace of mind.

In just cautious of ordering 4 injectors for £500+ for nothing, but I guess it's a preventative measure.

Offline Pudding

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #3 on: November 19, 2021, 05:32:00 pm »
You can't really tell just by looking at them unfortunately.  They can be 'recovered' with a rebuild and flow test but in all honesty, even that is just prolonging the inevitable.  The injectors in these engines are a service item I'm afraid, usually last 80-100K miles before one drops out permanently, sometimes sooner.  Depends on the driving style.

When an injector(s) goes, it's usually only noticeable at idle and light throttle, and generally smooths out with more rpm/load.

What you could do in the meantime is try some LiquiMoly 'fuel injection system cleaner'.  It's about £7 on Amazon and if the injector wakes up using that, it's a good sign it's on it's way out.  It's some kind of paraffin chemical by the smell of it, which will have lubricating properties, which can help free off sticking injector valves.

As for oil on the plug, that really isn't a good sign sorry to say.  That only happens when too much oil is getting into the combustion chamber, and if it's oil build up causing the spark cut.....you'll need to investigate the engine for mechanical wear/damage.

I think it's a coincidence about the CAN bus.  It has no direct influence over the fuel and ignition control.  FWIW, I tried a canbus update to fix a battery drain issue with an RNS510, but it caused more problems that it solved and I put the original gateway back in.  I later discovered the battery drain issue can be solved with a software update in the radio itself!



2007 ED30 | 2009 TDI 140

Offline Birty_

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #4 on: November 19, 2021, 05:41:33 pm »
You can't really tell just by looking at them unfortunately.  They can be 'recovered' with a rebuild and flow test but in all honesty, even that is just prolonging the inevitable.  The injectors in these engines are a service item I'm afraid, usually last 80-100K miles before one drops out permanently, sometimes sooner.  Depends on the driving style.

When an injector(s) goes, it's usually only noticeable at idle and light throttle, and generally smooths out with more rpm/load.

What you could do in the meantime is try some LiquiMoly 'fuel injection system cleaner'.  It's about £7 on Amazon and if the injector wakes up using that, it's a good sign it's on it's way out.  It's some kind of paraffin chemical by the smell of it, which will have lubricating properties, which can help free off sticking injector valves.

As for oil on the plug, that really isn't a good sign sorry to say.  That only happens when too much oil is getting into the combustion chamber, and if it's oil build up causing the spark cut.....you'll need to investigate the engine for mechanical wear/damage.

I think it's a coincidence about the CAN bus.  It has no direct influence over the fuel and ignition control.  FWIW, I tried a canbus update to fix a battery drain issue with an RNS510, but it caused more problems that it solved and I put the original gateway back in.  I later discovered the battery drain issue can be solved with a software update in the radio itself!
Thanks so much for your knowledge!

Yeah I thought it was a coincidence but I'm just going to stick the old one in for a peace of mind.

Yeah I mean they haven't been changed in 150K albeit a clean and service a year or so ago. Maybe it's just worth changing them out, I do plan on going for a stage 2+ at some point so it's probably a good idea anyway.

I must say, after a good drive to and from work today it seemed much better. Before it was a fairly violent misfire but it's fairly smooth now but still misfiring none the less. I'll give that injector cleaner a go, it might just confirm my suspicions.

With the oil on the plug, I think it might be the gasket. Only started occurring following a gasket change so maybe it's not seated right.

I'll stick some new plugs in and some injector cleaner the weekend.

Again, thanks for your help.

Sent from my Pixel 6 using Tapatalk


Offline Birty_

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #5 on: November 21, 2021, 02:51:45 pm »
You can't really tell just by looking at them unfortunately.  They can be 'recovered' with a rebuild and flow test but in all honesty, even that is just prolonging the inevitable.  The injectors in these engines are a service item I'm afraid, usually last 80-100K miles before one drops out permanently, sometimes sooner.  Depends on the driving style.

When an injector(s) goes, it's usually only noticeable at idle and light throttle, and generally smooths out with more rpm/load.

What you could do in the meantime is try some LiquiMoly 'fuel injection system cleaner'.  It's about £7 on Amazon and if the injector wakes up using that, it's a good sign it's on it's way out.  It's some kind of paraffin chemical by the smell of it, which will have lubricating properties, which can help free off sticking injector valves.

As for oil on the plug, that really isn't a good sign sorry to say.  That only happens when too much oil is getting into the combustion chamber, and if it's oil build up causing the spark cut.....you'll need to investigate the engine for mechanical wear/damage.

I think it's a coincidence about the CAN bus.  It has no direct influence over the fuel and ignition control.  FWIW, I tried a canbus update to fix a battery drain issue with an RNS510, but it caused more problems that it solved and I put the original gateway back in.  I later discovered the battery drain issue can be solved with a software update in the radio itself!
So I've pulled the plugs again. See attached photo, they don't look great. You can see which is cylinder three, like I said before I'm not overly mechanically minded so not sure what it's saying but doesn't look right.

I've changed them out anyway, but still missing on idle.

Thanks in advance

Sent from my Pixel 6 using Tapatalk


Offline Pudding

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Re: Canbus gateway upgrade - Multiple cylinder misfire & cylinder three
« Reply #6 on: November 22, 2021, 11:36:43 am »
1, 2 & 4 are the typical grey colour you normally see in these engines.

As for number 3, when you said it was oily, I thought you meant it was soaked in the stuff.  That looks dry? 

But anyway, that's clearly the cylinder with a bad injector!


2007 ED30 | 2009 TDI 140