Hi people I have a Subaru wrx turbo,
I have recently fitted a sti engine and it also had
Simtek Ecu fitted and mapped by steve stimpson.now recently
When I boot it the car seems to miss fire and starts backfiring,
Any ideas as to what it could be it seems to only do it if I really boot it and
Backfires terribly any help would be appriciated regards ben

 

Forgot to mention it's a my95 classic

 

Headgasket? Had similar issue turned out to be headgasket.

Coilpacks? this may be due to a crack.

Spark plugs arent gapped properly as this can causes issue.

 

coilpacks huge probs on v1/2 although usually more a miss then backfure.



Maybe timing has slipped a tooth.

 

The car runs absolutely perfect when I don't boot it but once I start booting it then it starts to get worse,normally around gear 3,4,5 . I'm sure when the car was being mapped I was told the plugs ain't the correct ones they were Halfords plugs but would this cause that problem it's a backfire,splutter but you can hear it banging away. I don't think it's head gasket tho

 

have you got a full decat exhaust system and does it do between gear changes

 

Yea full de cat and stanless uppipe aswell and no it only does it when my foot flat to floor

 

Coilpacks most likely. Pull them off and look for cracks, replace with new age coilpacks or V3/V4 single coil and wires if you plan to keep the car for a while. There are threads on Scoobynet and Nasioc about the conversions.

 

Could be a burnt/carbon'd valve?

 

Let the OP start with the simple things. A burnt/carboned valve would probably cause idle issues as well especially on cold starts.

 

Ill put a beer bet on it being coilpacks