Cylinder 3 misfire help!!

[xodia]

Hey guys,

I have a mk5 tfsi AXX which has just recently been stage 1 mapped by niki at r tech! The car was a bit down on power before mapping and niki diagnosed this as surface cracks in the turbo, fair enough i spose.. Anyway, maps on and i love the power!!

I am however, getting quite a few misfires which started about a month after the map and have steadily gotten worse over the last few weeks.

The misfire always seems to be cylinder 3, checking misfire counters with VCDS shows cylinder 3 is misfiring on idle and on load.

I have swapped coilpacks round and spark plugs round to see if the misfire follows either, which it doesnt, it stays on cylinder 3 all the time.

I have since logged a few runs, including boost pressure, fuel rail pressure specified vs actual, air mass flow, the only thing that stands out is that just before the car misfires the fuel rail pressure drops from 120 bar down to about 90 then returns up to 120 bar

It has a very rough start, the car feels like its badly misfiring then evens out.

I have changed the cam follower.

I have had some weird faults shown by VCDS, the EVAP system keeps coming up as a fault, but i cant seem to see a pattern, this is quite random,
Straight after a full on misfire and the eml light flashes, i scan the car and it comes up with cylinder 3 and random/multiple misfires detected.

I have also had a fuel cut out a few times and has said fuel pressure regulator and fuel level low???

I have a feeling it could be injector on cylinder 3 and the n276 valve on the HPFP??

Would this my best places to start looking??

Any help you guys can give will be rewarded.. With various emoticons!

By the way, not dissing r tech at all!! I asked a question about the map recently on VAG TALK facebook page and one guy got completely the wrong idea! I would never take my car ANYWHERE else! Niki took such care and attention to my car i wouldnt trust anyone else anywhere near it!

[Hurdy]

A few guys have had similar issues and ended up being the injector. They did try injector cleaner first and it cured it temporarily, but the misfire ended up coming back. Sounds like you've done a decent diagnostic on it. 

[xodia]

Hi hurdy,

It is what i was thinking, i didnt want it to be that just because of having to take the inlet manifold off to get to them! But, it would mean i can clean the valves out at least!

Thanks for the feedback on my diagnosing, i wanted to give as much info as possible, as i know without it, its like finding a needle in a haystack with VW lol

[topher]

i'd say you're spot on the valve and injectors are known to misbehave.. although i'd be reaching for the compression tester first just to make sure. its not quite the symptoms for low compression but its a ton quicker than taking the manifold off

[xodia]

Just figured out VCDS has an output test option for the injectors, 1,2 and 4 click fine, and guess what.... Number 3 is no noise at all! Pretty much all but confirms it i feel

Yay, now the fun job of removing the inlet mani!

[Hurdy]

Awkward part of removing the mani is the support bar underneath. Sooo much of a pain it got left off when the mani was put back on.

[xodia]

Hi all, in case this helps anyone else, this turned out to be the injector, which I've now replaced, and f****k me! It's like a different car!!! Ever since I got it it's always been a bit noisy on idle and had a bit of an engine judder, I just put it down to the way it is, how wrong I was?! God! Just wow!! I am certain it's making more power than it did when I left r tech! Loving the TC light coming on in 2nd all the time!! it never used to do that!!!! Thanks for the advice and pointing me in the right direction!!

[Saint Steve]

Great news. Mine was exactly the same but injector 4.