Took a run up to Donington at the weekend and the car was running a bit poorly. All the problems I'm going to describe are intermittent so I'm assuming something is slowly breaking down.

Has had a juddering whilst accelerating between 2&4k for while. Checked boost hoses for oil etc and all clear.

Also started getting a slight 'misfire' both whilst accellerating and whilst cruising, but only seems to happen off boost at around 1750 or 2500 rpm, when accelerating it feels like a flat spot, but if I'm cruising the car will 'hiccup' and then carry on as normal.

Finally the idle is abit lumpy in that it seems to miss a beat every few second. It also seems to take a couple of seconds to settle when you stop.

Got a new MAF about 5 months ago so ruled that out. No CEL, drop in revs when it happens and its run on optimax or SUL if I'm stuck although I filled up with this new shell v-max? or whatever it is this weekend.

Car has an STi filter, magnex cat back exhaust and forge VTA dump valve. The DV has made no difference, its the same with this or the standard recirc.

My guess is the plugs or coils breaking down, I'll be doing the plugs when my new hoses arrive in the next couple of week because I have nmy doubts about the FSH.

Any other possibilities before I get a couple of spare coil packs

 

Oh, and its more pronounced when it's cold with a definate flat spot at about 1750 rpm. The top end sounds a little rattley, although you can only hear it when you are out of the car and when the idle is right down to 750rpm and not at cold idle or when the revs pick up, but that is the injectors to me. Could be tappets though.

 

Anyone?

 

Interesting this as i've got exactly the same problem at the moment

 

I've got a new set of plugs and some second hand low mileage coils to throw on which I'll be doing in the next couple of weeks, if that doesn't do it I'm stumped. Hopefully it'll cure it.