Heavy sputtering around 5k rpm when accelerating hard

[Reeceyy]

I did make another thread earlier this month but the problem persists.

When giving it full throttle, the car sputters around 5000 rpm as if it were bouncing on the rev limiter. When giving it gradual throttle, it doesn't happen. Only when accelerating hard. It's very frustrating this. 
I've changed the following. Bank1/sensor1 oxygen sensor. Checked camlobe and cam follower for wear. No wear and cam follower was replaced. Changed the piston in the HPFP to a vis one. The car was fine when all that was changed. I believe the oxygen sensor made the difference. But the problem is back! And this time it seems worse than ever. A mechanic said he graphed the fuel pumps and turbo and they are all running fine. I'm lost for what this could be. He said that he reckons it could be a stretched cam chain but I'm not too sure. It's a lot worse when the engine is hot!!

The car is 290bhp stage 2 with S3 intercooler, downpipe, Vis piston and ramair induction.

Please, if anyone has any idea of what this could be, I would appreciate it greatly if you could let me know.

Many thanks.

[mjmallia]

Have you carbon cleaned the intake valves?

Spark plugs?

Fuel filter?

[ZoliWorks]

Log lambda control with VCDS. I've got the same issues past 5k rpm because I'm running K04 boost on k03 injectors and the ECU is trying to prevent engine damage due to running too lean. My lambda is maxed out at 25% so I've got constant loss of power as the ECU is trying to figure out what to do.

[Reeceyy]

Have you carbon cleaned the intake valves?

Spark plugs?

Fuel filter?

Fuel filter was changed last month.
Spark plugs changed to NGKs last month
Coilpacks changed too.
I've also changed the low pressure fuel sensor the lower one on the HPFP which is on the fuel rail. None of this made a difference.

I haven't carbon cleaned the valves yet though but I've been told that carbon build up shouldnt be that bad because it's petrol and not diesel.

[Reeceyy]

Log lambda control with VCDS. I've got the same issues past 5k rpm because I'm running K04 boost on k03 injectors and the ECU is trying to prevent engine damage due to running too lean. My lambda is maxed out at 25% so I've got constant loss of power as the ECU is trying to figure out what to do.

I suppose it's more or less the same problem as what I'm going through then. The only difference is that I have k03. The map is maxed out though. What's the cure for this then? Have you sorted the problem out?

[mjmallia]

I've also changed the low pressure fuel sensor the lower one on the HPFP which is on the fuel rail. None of this made a difference.

I haven't carbon cleaned the valves yet though but I've been told that carbon build up shouldnt be that bad because it's petrol and not diesel.

Direct injection petrol like our TFSI is the worst for carbon fouling.....loads of info about it

It can cause misfires like mine had where the carbon stops the valves sealing..........and also a total loss of top end power like my wifes golf had, where the valves were like ice cream cones, but sealing and no misfires.....zapping the power

[mjmallia]

My wifes was similar to this on an FSI MK5 Golf



My TFSI GTI was a little less but the carbon was not allowing the valves to seal creating misfires.

[Reeceyy]

I've also changed the low pressure fuel sensor the lower one on the HPFP which is on the fuel rail. None of this made a difference.

I haven't carbon cleaned the valves yet though but I've been told that carbon build up shouldnt be that bad because it's petrol and not diesel.

Direct injection petrol like our TFSI is the worst for carbon fouling.....loads of info about it

It can cause misfires like mine had where the carbon stops the valves sealing..........and also a total loss of top end power like my wifes golf had, where the valves were like ice cream cones, but sealing and no misfires.....zapping the power

So it's most probable that my problem is carbon build up? The injectors are dirty and are not feeding the engine with enough fuel?

Is a carbon clean expensive? Would I have to change the injectors too? Is there a way of knowing that there is carbon build up before taking the inlet manifold off?

[Reeceyy]

The sputtering is now worse than ever. It don't even make it to the end of the rev range, it's as if It were bouncing off the rev limiter at 5000rpm. Most mechanics don't have a clue what this is as they just rely on their diagnostic machines and they are not giving them the proper fault code.

[mjmallia]

So it's most probable that my problem is carbon build up? The injectors are dirty and are not feeding the engine with enough fuel?

Is a carbon clean expensive? Would I have to change the injectors too? Is there a way of knowing that there is carbon build up before taking the inlet manifold off?

It is time consuming and took me a day at home to dismantle and clean out the carbon while the injector tips were soaking in petrol.

New injector seals are about £100 for genuine ones
New manifold gasket about £20
A variety of picks and wire brushes etc
General tools to take the manifold off
Time

If not the cause, it will def help make the engine run a lot better.

Faulty/lazy injectors will not help either

[GreigC]

I’d say your injector(s) are the issue. Common symptoms are under load it can feel like lumpy/misfire also sitting at idle it can feel like it’s misfiring (usually a very minor wobble) also injector(s) cause intermittent cold start spluttering. It’s very common on these engines and although can be refurbished or bought second hand most of the time a new set are required about £1000+ often left and when the next owner has went though coils, plugs trying to find the issue they leave it because of the cost. A carbon clean will also help and usually makes sense to do when your replacing the injectors but again comes down to cost/time.

[ZoliWorks]

I’d say your injector(s) are the issue. Common symptoms are under load it can feel like lumpy/misfire also sitting at idle it can feel like it’s misfiring (usually a very minor wobble) also injector(s) cause intermittent cold start spluttering.

Lol I have all of those symptoms. Another thing the car does is lose all rail pressure after stopping the engine in just under 20 minutes. Like literally no pressure when opening the bleed valve. When I open the door so the electric fuel pump kicks in, i can hear how it's pushing out bubbles from the system. Most tuners I spoke to said my map is poorly done cause too much boost for K03 injectors but the tuner himself says it's the injectors that are the problem.

I suppose it's more or less the same problem as what I'm going through then. The only difference is that I have k03. The map is maxed out though. What's the cure for this then? Have you sorted the problem out?

Carbon buildup and/or injectors most likely. I'd log lambda just to see what the values are. For me, I've carbon cleaned my intake valves back when I bought the car last year so for now the solution to my problem is to fit some proper, brand new K04 injectors and remake the map.

[Reeceyy]

Sorted! Ended up being a MAF sensor! I went back to the guys that remapped it. It was misfiring in all cylinders. I even cleaned the MAF  a few weeks back but it made no difference! It has to be changed. At the moment it's unplugged but going as well as ever!! I finally got my car back!

Just don't ever take a mechanics word for it. I was told that it was the cam chain. This was never the cam chain and I knew that. I had my lambda sensor changed because that was coming up in their diagnostic tool. It wasn't that either. But you end up paying for it.

The only positive that's come from this is that I changed the piston in my HPFP!

Just another note. I had 11 engine faults and not one of them was related to the MAF sensor. Be careful here because mechanics rely on their diagnostic tools nowadays instead of their mechanical knowledge. I had 2 lambda sensor faults, I had a boost pressure fault the p0229 one. I had the multiple misfire fault and misfire in cylinder 1,2,3 and 4. I also had a low fuel pressure fault.

Good luck guy and thanks for the input. Much appreciated.

[ZoliWorks]

Nice, glad you sorted it out. I'll also try getting a new maf, even tho mine doesnt seem to be giving me issues.

[GreigC]

I was well off! Glad you got it fixed man.