The misfire counter only shows full misfires. It may not show partial misfire. It can say all is well when it ain't.

My coil no.3 started slowly to fail, it was slightly noticeable around 3500 rpm. There were no errors stored but in block 015 the value was jumping like crazy. This was no way near violent as in cossie case.

I have to say it sounds like a fuel pump to me too. 3rd 4th gear says so... if the fuel pump has done over 60.000m and every now and then its driven under the orange light, then I would bet this is it

I have to say it sounds like a fuel pump to me too. 3rd 4th gear says so... if the fuel pump has done over 60.000m and every now and then its driven under the orange light, then I would bet this is it

I have 2 vrs's, both run 1.4bar and i've swapped the pumps over.

The vrs with the issue still has the issue, the vrs without the issue, still doesn't have the issue.

That suggests to me, the fuel pump isn't the problem.

Did you try swapping the coil packs yet?

Did you try swapping the coil packs yet?

Not yet, as there only a couple of months old.

I know mine was very sensitive to misfire at high RPM and full boost which was cured when I went to bolt downs and smaller gap on plugs. I still had to regap the plugs every couple of months as well as the missfires would start to creep back in as the gap opened. Now I use the mk6 2.0 T coils and a bigger gap and have no issues At all. Swapping coil packs over is a fairly easy job (apart from number 4) so worth a try as even new coils can be goosed

I know mine was very sensitive to misfire at high RPM and full boost which was cured when I went to bolt downs and smaller gap on plugs. I still had to regap the plugs every couple of months as well as the missfires would start to creep back in as the gap opened. Now I use the mk6 2.0 T coils and a bigger gap and have no issues At all. Swapping coil packs over is a fairly easy job (apart from number 4) so worth a try as even new coils can be goosed

I will change the fuel filter over later today, and if that doesn't cure it, I will swap the coilpacks with the ones from my other vrs that were brand new last week.

If that doesn't cure it, then I will swap the map sensors over, and if that still doesn't fix it, then I think I will giveup.

Have you inspected the coil wiring loom as any breaks will cause arc to the head. I wrapped mine individually with electrical tape

Have you inspected the coil wiring loom as any breaks will cause arc to the head. I wrapped mine individually with electrical tape

Skoda wrapped it up when the coils were done under the recall.

I used to get a sudden boost drop at 5500ish which was cured when I improved the airflow into the standard air box but you have tried with a CAI direct to the maf so that should rule out that.

So your dv, is it under the control of the n75 or have you bypassed it to just pull VAC off the manifold?

So your dv, is it under the control of the n75 or have you bypassed it to just pull VAC off the manifold?

N249 has been removed, as has N112, SAI and I have also done the vac simplification and evap simplification mods.

The dv is direct to the vac from the manifold.

So today I have done the following:

Fitted new fuel filter

Swapped the map sensor from the other vrs (luckily I had an adaptor with my pro alloy front mount for both sizes of map sensor, as the other car was the smaller one)

Swapped the coil packs from the other vrs (new last week)

Swapped the fuel pressure reg from the other car (4bar instead of 3bar)

Nothing has changed, still does exactly the same thing.

I also tried a different map on the car (runs less boost), but it still fluctuates a bit, between 0.7 and 1bar and it still goes funny around 5500rpm (although there wasn't an actual misfire).

I did have a fault code log today (twice) which was the lambda sensor for bank 1, and I cleared it both times and it's not come back again, but I am sure that is due to the decat.

When logging 015, 016 in vagcom it did log 2 misfires on cylinder 2 on one run, but on further runs no misfires were logged.

I am rapidly running out of ideas now, tomorrow I am going to remove the injectors, and swap them over, and if it's not that, I guess i'll have to do a compression test.

I did wonder if the N75 could be playing up, as it was disturbed when I removed the standard TIP and fitted the Forge TIP (which is when the issue started), but I can't see how or why it would cause the misfire.

To be clear the follow have been swapped this week with known good working items:

Maf sensor

Map sensor

Coil Packs

Fuel Pump

Fuel Pressure Reg

Fuel filter replaced

Spark plugs replaced

CAI with K&N swapped with stock Airbox

Ontop of that, I did the full N249 and N112 removal (only sensors left plugged in, but no hoses connected to them), SAI was removed last week, vac lines have been reduced to the minimum needed and are new lines, the evap system and suction pump system were simplified also.

Have you tried regapping your plugs as karlbar2k said? I had the same problem, gapped them to 0.7 and it was sorted. Not sure what the gap is for stage 2 cars.

Have you tried regapping your plugs as karlbar2k said? I had the same problem, gapped them to 0.7 and it was sorted. Not sure what the gap is for stage 2 cars.

No not tried that, but blowing spark out won't cause the boost to fluctuate.

Ok, can knock be logged in vagcom and if so, does anyone know which measuring block(s) need to be logged ?

Also is it possible for a ko3s at 1.4bar to max out a good fuel pump ?

Could the N75 be causing all the problems, buy not holding steady boost, could the ecu just give up and drop the boost and becuase it's at high revs when it does this, cause a rich (or lean) misfire ?

Would / could a faulty lambda sensor cause these issue's ?

No the fuel pump should be good. Mine runs 1.4 bar and no fuel starvation. Like I said the issue I had at the top end was tip collapse due to vacuum caused by not enough air in. Improving the intake stopped that. And not it revs to 6500 no problem. The worst boost flu that ion I had was with my original map which was too aggressive at the start which started an oscillation. Just backing it off a bit smoothed it out and it now holds better dropping from initial spike of 21 down to 14 at 5500

No the fuel pump should be good. Mine runs 1.4 bar and no fuel starvation. Like I said the issue I had at the top end was tip collapse due to vacuum caused by not enough air in. Improving the intake stopped that. And not it revs to 6500 no problem. The worst boost flu that ion I had was with my original map which was too aggressive at the start which started an oscillation. Just backing it off a bit smoothed it out and it now holds better dropping from initial spike of 21 down to 14 at 5500

What I don't understand is that before I fitted the forge TIP, the car ran perfectly fine at 1.4bar.

If it wasn't such a ball ache, I would remove the forge TIP and refit the stock one.

I have had my tip in the shed for over a year now. Ever since I sorted out the intake issues I havent bothered.

I tried one of the uprated n75 on mine but ended up going back to the standard one with the map Tweak. So the only bit you haven't tried is the n75? Are you sure all the tip connections are solid?

I have had my tip in the shed for over a year now. Ever since I sorted out the intake issues I havent bothered.

I tried one of the uprated n75 on mine but ended up going back to the standard one with the map Tweak. So the only bit you haven't tried is the n75? Are you sure all the tip connections are solid?

I have double checked all connections to the TIP (the bottom 1 by the turbo is blanked off now, due to the evap simplification), the pcv is tight, as I have pulled the hose off it today to see if the car was breathing heavy (it wasn't), the dv is tight (again checked this as I had to remove it to get to the N75 to check that was tight) and the small pipe at the top is blanked off as the pipe that went into it has been removed now.

The only things i've not changed is the N75 as I don't have a spare (my other car has an AVCR so the N75 was removed and mapped out) the injectors and lambda sensors.

Ok thinking about this more (as it's doing my head right in now).

The boost used to hit 1.4bar and hold for a bit then drop back to 1.3ish.

Now it hits 1.45 with the airbox and nearer 1.5bar with the CAI, and then drops back to a bar, and up to 1.45ish and back before dropping right off.

Is it possible that with the TIP it's now hitting overboost ?

Does the 1.8t have a soft fuel cut if constant overboost occurs ?

Ok I don't know if these help at all, but a couple of logs from today.

log1.CSV

log2.CSV

if you have bypassed the ECU's ability to control boost with the n75/wastegate and DV then it can also use the throttle but dont think it cuts fuel, athough I am sure there is bound to be someone lurking that knows for sure. Overboost cut is usually sudden but the oscillation may be what is causing it.

On this car, the N75 is connected as normal.

It's my other vrs that doesn't have the N75 anymore (hence I can't swap them over to see if anything changes).

Ok my mate kindly lent me his N75 to test today, and it hasn't changed anything, so that rules out it being an N75 issue too.