my impreza has started to develop a misfire when it gets to a bar of boost
any idea what could cause it? it is mapped for 1.2 bar

 

Put a new set of pfr7b spark plugs in and gap the to 0.7mm.

 

it had a set of those fitted 3-4 months ago and has been fine until a few days ago

 

im not trying to worry you but mine did that for about 3 months then a con rod snapped and mashed all the engine casing up inside, the missfire was caused on mine because the conrod was bent, not giving the right compression, causing a slight missfire, i would do a compression test just to make sure, it ended up costing me a lot more when it snapped, than it would have if i changed it, good luck jons.

 

bugger

 

what year?

most likely spark related as suggested.. if an early car then could be coilpacks, or ht leads.. also clean and regap the plugs.

compression issue would give a lumpy idle too

Simon

 

it is a 1996 wrx ra. idle seems to be fine. will check the plugs.

 

i had a 1996 sti last year and mine developed a missfire under hard acceleration at about a bar of boost and i replaced the large coil pack on top of the inlet manifold and that cured the problem you could try that??? thats unless u have the earlier type with the four single coil packs?? worth a try. hope this is of some use to you.