Missfire
 

Its a version 2 Sti Ra and under hard boost the car missfires and hessitates. I have changed the plugs, cleaned the boost solenoid where no dirt came out at all even though from doing a search here I was expecting loads of crap from it.

Sometimes when it missfires I get a loud pop from the exhaust. If I gradually apply the boost its perfect bit if I slam the loud pedal quickly It happens.

Whats next?
Cheers.

I had exactly that problem a few weeks ago, just as you described. On my car, the fuel pressure vacuum pipe had popped off, it's the pipe that goes from the fuel pressure regulator to the inlet manifold, just in front of the turbo. Although if you've cleaned the boost solenoid you probably would have spotted if it was unplugged. Worth checking though.

Thanks Jamie but they are all fine, just double checked a couple of minutes ago after reading this.

I'll put my money on one or more of your coilpacks being fooked!

They will tend to display their being faulty, as a misfire when under load.

Richard

Maybe it's the MAF sensor - if you disconnect it with the engine running it should stall. If it keeps running then the MAF is definitely dodgey.

Another misfire I had, although not as bad, was caused by dirty/damp HT leads, I just cleaned them and gave them a blast with WD40.

I had same problem under heavy boost...re-gapped plugs to 0.6 mm and sorted the problem...runs at 18psi now with no problem..had it over 20 at one point and no missfire.

Highr the boost..smaller the plug gap

Pound to a pinch of Poo its the Coil Packs. Take em out Peel back rubber and look for hairline cracks at the tip of them. Be careful fitting them back in. Most of the time it is caused by overtightening them.

Good luck

Gavin