Engine Running Rough Hi Rpm

[baf6]

Hi guys, im having a problem that happens on occasions, when im givin the F6 a bit of stick and back off the engine runs rough and loses power, usually just back of for a bit and it comes good, mostly happens in 4th or 5th gear.

whats the most likely cause of this, valve springs, coil packs? any other ideas?

I've done a bit of searching and thinking valve springs, if it is the case, what are the best value valve springs, noticed theres quite a range.

Brad.

Edited 07/05/11 02:27 AM by baf6

[Mr_4.0]

How long is it rough for? If u try and slowly accel while it's rough, what happens?

[Panda Eyes]

valve springs will do that on hi revs. a sedan with no surge tank will do that if fuel level is under 1/2 tank. old plugs will do that under load.

[baf6]

its rough untill I back right off and slow down, if I accell slowly it runs rough like it's not running on all cylinders.

Its a ute but I do get fuel surge under 1/4 tank, plugs were replaced recently by tuner

[Kroozin]

mine does the same.. I'm led to believe it is the valve springs and they need to be replaced with aftermarket springs I think some guys are using crow cams springs,etc..$$$ .

What is the worst case scenario if encountering valve float here and there after a big rev like baf6 has said?

[baf6]

rapid have springs for $279, think I'll get them and see how I go

retune too, might see the power I should be, with a lil luck

Edited 10/05/11 08:58 AM by baf6

[ratter]

.

What is the worst case scenario if encountering valve float here and there after a big rev like baf6 has said?

dropping a valve into the cylinder and smashing the piston, block and cylinder head