Hi guys- hope someone can help cos I'm tearing my hair out over this one....

I have been plagued by a misfire on my 96 STi R/A, which only makes itself apparent in 1st and second when trying really hard.

Sounds like popping from the exhaust, like on the over-run. Normally I love the sound but not when accelerating! It also momentarily loses power when this happens.

I have changed the plugs to HKS iridiums and gapped them to .7. I have also removed the induction kit and dumpvalve to eliminate these.

I have checked all the coilpacks and they seem to be fine (I had one brand new one with which to compare the rest). Have also cleaned out the bosst control solenoid, cleaned the hot wire MAF and checked and cleaned the Cam position sensor and crank angle sensor.

Now I'm standing here scratching my head- the AFR is showing its fuelling ok (poss a little bit rich) and boost doesn't seem to be spiking. I'm starting to suspect a fuelling problem but your help would be appreciated!

cheers,
simon

 

have you tried fitting the little Ht insulator mods on top of the plugs, prior to sitting the Ht leads back on?
Was an early mod for misfire on early turbo's, give it a whirl, might cure, who knows.
Gen scoob pt No is: 22489AA030

 

Had a misfire on my 94wrx which turned out to be the coil packs. Like you I just got one to try replacing them one at a time, but the misfire persisted. Only when I changed them all together did it cure it. I guess they probably all wear out at the same rate !?
Mark

 

I think that changing one at a time probably displaces the signal from the others.
or something like that...

 

I seem to get a small hesitation at times in third at around 4K,
this has only been apparent since filling up at ESSO during the last few days????

Is it normal for the boost to feel mildly "steppy" when the engine is cold? Obviously I am not driving it hard until the car has warmed up!!

No mods unfortunately - just ITG at the moment.

 

best way to go to cure a missfire on these little monsters is new ngk pfr7b plugs gapped to 0.7 and the 3 point earth mod cured mine even though the ends of the coil packs are breaking up!!!

mark

 

Mark, Can you let me have details of the earth mod please.
cheers,
simon.

 

There are no excuses for missfire, large voltages are involved so it is inevitable that the standard coils wear out. Its happened to lots of peeps on here me included, the grin I had when first driving a scoob made a welcomed return to my dish when I fitted the cheap as chips (Aus) Bosch Mec coils. If you dont mind paying waaay over the odds take it to subaru and get new ones. If you want a quick fix only to have the same thing happen in 3 months get some from a breakers. Hmmm I wonder if theres an answer lurking in there somewhere.......
For further convincing goto
http://www.scoobynet.co.uk/bbs/thread.asp?threadid=149358

 

http://www.scoobynet.co.uk/bbs/thread.asp?threadid=146853

here this should help you

mark

 

thanks again