S3 random misfire cyl 4 misfire.

[PhantomBlackS3]

Hi everyone,
I own a phantom black s3 sportback 8P with a stage 1 remap and a catback miltek. Great car most of the time...but im looking for some advice.
I do apologise if this has been discussed on another thread but i dont fancy hijacking someone elses post.
A few weeks back i experienced a misfire. This was noted in cylinder 4 when my car was mapped and i kept note of it until the day it misfired.
A week later i change the coil packs and spark plugs for genuine parts (no ebay stuff) and the car misfired again, my mate had a look at it and put it down to under tightening of the spark plug in cylinder 4 on my part, so he done a pressure test on all four cylinders each coming back fine with the exception of cylinder 3 showing a tiny bit low.
Fast forward a week and im heading home and give the car some welly, major misfiring, engine management light and the car sounds like a tractor...i nurse it to my parents house, sit for 15 minutes then bite the bullet amd decide to make my way home.
Low and behold the car starts fine no light and no noise...got it on vcds and the fault codes showed a random/multiple cylinder misfire and a misfire on cylinder 4...again.
Since the engine management light scenario the cars driven fine in sports mode under full load on various occasions until this afternoon pulling awwy from lights under light load and i feel a misfire.
I should note ive had a carbon clean done, which i know most people will say is a waste of money but i got it done anyway. And i also added a can of 44K to a full tank which has been in it for the last week or so.
I need any help at all, any pointers will be welcomed with open arms, my mate reckons a sticky valve or weak valve spring, but failing that i dont have a clue what else could be causing this.
Cheers.

 

[samuelh_888]

If it was noted at the remap, why did you continue with the remap.

Is 44k an injector cleaner?

Injector cleaner isn’t ideal as it breaks down all the crap in the tank, lines, filters and injectors which can in-turn block the injector filter baskets.

If you haven’t already it would be worth giving the injectors an ultra-sonic clean and test their spray.

Until then, don’t boost it.

 

[PhantomBlackS3]

If it was noted at the remap, why did you continue with the remap.

Is 44k an injector cleaner?

Injector cleaner isn’t ideal as it breaks down all the **** in the tank, lines, filters and injectors which can in-turn block the injector filter baskets.

If you haven’t already it would be worth giving the injectors an ultra-sonic clean and test their spray.

Until then, don’t boost it.

It was assumed that it was a coil pack and i decided to go ahead with it, assuming however has seemed to be the downfall of my decision.
Ive managed to get it looked at this wednesday/thursday, so hopefully he can diagnose exactly whats wrong.
What i cant figure is why its so intermittent, there isn't sort of pattern for it misfiring, all occasions have happened under different circumstances.
I can arrange to get that done, and i'll try not to drive it at all.
And yes 44k is a fuel and injector cleaner.

 

[SootySport]

I would say your boost pipe has split or come loose due to the extra power.
Sounding like a tractor is the giveaway symptom.

 

[PhantomBlackS3]

I would say your boost pipe has split or come loose due to the extra power.
Sounding like a tractor is the giveaway symptom.

It really did sound like a tractor mate, however when i stopped the car for around 15 minutes and restarted it there was no awful noise or engine management light.
If it was a split or loose boost pipe would it constantly sound awful? As this was only for around 10 to 15 minjtes the car sounded like that.

 

[PhantomBlackS3]

Hi all, sorry to revive an old thread. But bit of an update on the issue, a friend had the car on friday jst last week and could not find any signs of a weak valve spring, sticky valve or anything untoward that would cause the misfiring, done a road test and logged the live data all injectors firing fine and the way they should be. His best guess was some sort of blockage in the injector in cylinder4. I did note when i picked my car up i got a service done on it at around 65k and the fella who done the service told me that he did not think the fuel filter had been changed in that 65k miles, the residue inside it was brown and quite unpleasant, i also dont know which kind of fuel the previous 1 owner used. Would i be wrong to assume that a combination of non premium fuel, an unchanged fuel filter, the fact that i recently have ran my fuel quite low in the tank (which is laziness on my part) and the stage 1 remap demanding more fuel could all play a major part in some unwanted residue for lack of a better name, being put through the fuel lines and into the injectors? And could a blocked injector cause an engine management light at full throttle at around 6400rpm?
Thanks to anyone who reads the whole thing lol.