CEL Code - P0301 - Cylinder 1 Misfire

[brad]

You still have fuel vapour in the intake system via the charcoal canister and n80 valve.

Fair enough but it aint doing no good.

[Transporter]

So a compression test found it! The fault was caused by the build-up of sticky residue meaning the valves didn't seal properly when cold, causing low compression and a misfire.

A intake manifold clean has fixed it and the car feels smoother and revving easier as well.

Well, more like the build up behind the inlet valves disturbed the airflow into the cylinder, which was enough to cause the misfire under certain conditions. So, the compression test couldn't actually find it and mechanic told you what you wanted to here, which doesn't matter since it looks like they most likely fixed the problem for you, at least for some time.

[Mattlock]

Well, more like the build up behind the inlet valves disturbed the airflow into the cylinder, which was enough to cause the misfire under certain conditions. So, the compression test couldn't actually find it and mechanic told you what you wanted to here, which doesn't matter since it looks like they most likely fixed the problem for you, at least for some time.

Haha! Probably very true. He said that the misfire only happened when cold (as I had reported it) because once the engine had warmed up the gunk on the valves was sticky enough to seal everything up!

Their thoughts on the topic are very similar to those of Brad's in that VW DI engines are prone to this. In fact it was a Mk6 GTI the other week that had very similar issues that led them to fixing it with mine.

[themarvel2004]

Hey guys,

Had this happen to me on the weekend too whilst on my way back from the SA cruise (yes, I bailed part way through!) - got some mis-fires while pulling up-hill hard around 4k RPM.
Checked with my scanner and had P0300 & 0301 codes recorded.
Seemed to be running ok later that day with no issues, and same yesterday, but did have abit of a moment at low RPM (like 1800) on my way to work today (just a little bit of throttle when in 6th at around 60kph).

Car is at 100k km, and I don't think it has had a de-carbon done in any previous service (need to double check), and plugs were probably done 5-7 years ago also.

So - would you recommend that I first try a de-carbon process with something like the liqui-moly product?
Then do Plugs if still no joy?
Then do Coil packs if still no joy?

I think I also need to do my DV upgrade at some point soon (probably go a GFB DV+ kit, currently a RevC stock DV). Thought it was that when it happened actually (until I got the code details).

Is doing a carbon clean process just going to make it worse if it is the plugs or coils? Could I end up not being able to start the car at all?

Is there anything else to watch out for using these de-carbon spray packs at home?

Thanks!

[Mattlock]

When my Mk5 threw this error it was cleaned up by hand. I don't know if any cleaner was used on it. The second time it was a runner flap issue rather than deposit build-up.


Sent from my iPhone using Tapatalk

[themarvel2004]

So, checking my service records, plugs were done in 2011 @66k km, so I've only gone 35k since then. Guess it's unlikely to be that.
So try the de-carbon first then?

[themarvel2004]

So - ordered new coils, and bought new plugs. Turns out my Cyl 1 coil had a big flap of rubber torn - not sure how, but obviously it was leaking spark.



Runs perfect again - pulls smoothly without stuttering from low RPM.

[Snail Style]

Leaking spark? Hmmmm

[themarvel2004]

IE the current was finding an alternate path not through the spark plug.

[Snail Style]

That rubber seal just helps to stop water getting into the spark pot mate, it doesn't hold the spark in.