Cylinder 4 misfire

[DBXdarkangel]

Hey guys. My axx 2005 gti has developed a misfire on cylinder 4. When I drive it steady it's fine but when I floor it, it becomes hesitant and stutters. I've replaced all plugs with ngks that was already in and I've replaced coilpack 4 with a brand new one. Vcds logged the misfire on cylinder 4 before I changed the plugs and coil pack and its still logging it on 4. There was a fault stored as the usual bank 1 manifold flap and manifold motor so I've arranged for that to be replaced in two weeks time. But I'm not sure what's causing the misfire. I've took some photos of the fuel pressure but not sure what it's supposed to be?
Also my vcds won't let me check blocks 013 for Injectors as maybe it's that?

[muff1991]

Is it misfiring constantly? just at idle? under load?

Misfires are usually caused by: plugs, coils, air leak or injectors.

[mjmallia]

And carbon build up on the valves like mine was on warm idle

[DBXdarkangel]

Is it misfiring constantly? just at idle? under load?

Misfires are usually caused by: plugs, coils, air leak or injectors.

Its got a slight rumble on idle but missfires a lot when under load. Vcds shows it's just cylinder 4.
As I said I've changed all plugs and fitted a new coil pack on pot 4 (I originally swapped the old could pack from 4 to 3 hoping 4 would be ok and 3 would misfire but it still counted 4 with the issue)
It's going in my local garage next Thursday for a replacement inlet manifold and flap motor fitting. I've bought a brand new injector to fit on port 4 too but if you guys thinks it's something else I can send the Injector back?

[mjmallia]

If you are having the manifold off.....get them to carbon clean the intake valves while there.

It sounds like an injector or carbon issue to me.......but the manifold has to come off either way to inspect.

[DBXdarkangel]

If you are having the manifold off.....get them to carbon clean the intake valves while there.

It sounds like an injector or carbon issue to me.......but the manifold has to come off either way to inspect.

Can any garage do a carbon clean? Mine's a back street garage

[pudding]

Bad injector. May as well replace all 4. Doing one is a false economy.

I doubt it’s carbon fouling as that only happens when cold in stratified injection mode.  When hot and under load, the runner flaps are open and injection switches to homegenous mode.  You will only ever get carbon related misfires if it’s bad enough to screw up the stratified mode.

[DBXdarkangel]

Bad injector. May as well replace all 4. Doing one is a false economy.

I doubt it’s carbon fouling as that only happens when cold in stratified injection mode.  When hot and under load, the runner flaps are open and injection switches to homegenous mode.  You will only ever get carbon related misfires if it’s bad enough to screw up the stratified mode.

Replace all 4? Mine are 06F 906 036 A and £106 each. Don't fancy shelling out £424 If only 1 is bad. Vcds says it's only piston 4 it's missing on and the runner flap motor is dead so it might be just that. My garage says it's a 2hr job a d Labour is only £90 job done. Think I will get him to replace the faulty injector then if in the future the other ones go faulty I will replace the lot.

[pudding]

Well if it's only £90 labour, I would just fix the original fault first (flap motor) and go from there.

[DBXdarkangel]

Just got my car back from the garage and running perfectly now. He replaced the intake manifold, injector 4, flap motor and did a service too. Gonna run it on vcds tmr to clear any faults and scan it. He said there's not fault codes on there anyways.
Ticking over nicely now and very quick again. Very happy  :)

Gotta replace the seals on the vacume pump tho as that's leaking abit of oil. Easy job I reckon

[DBXdarkangel]

Offending injector

[pudding]

Yep, that's what happens to them.  Should have replaced all 4. You'll be going back in there again to one or more of the others soon.