hi all have just finished rebuilding a wrx front end needed bought as accident damage. i have done about 1000 trouble free miles then yesturday on the m1! i hit a problem i got done by a ford!!!!!!
i got hesitation on full throttle above 4k and a missfire with a slight backfire felt like fuel starvation have checked all plugs seems like no 4 was running alittle lean by the colour of the plug but the afr is reading in the green. if you accelerate slowly fine up to 5k in 5th
you gan hold revs at any rev range with the car not under load no hesitation.
the car has had full service upon completetion of rebuild fuel filter oil air etc..
any ideas i am well and truly stumped could it be a crank or cam sensor retarding the ignition, if i put the stethescope on it no det

 

Hi mate, you had any luck finding out what the was was on your car? as i have the exact same fault on my 99 wrx. I changed plugs, leads and maf. Now im just stumped dont knw where to look next.

 

just replaced more hks plugs fuel filter waiting for some replacement leads from magnacore amber performance is cool good guys have also been speaking with my local rolling road they say electrical i thought it was fuel but found i had a bad earth high resistance on the neg. so replaced that as well.
this is a pain in the ***

hope the leads will solve the problem it may have been some crappy fuel as i had to go to kent today she drove ok except if i planted it then was alittle stuttery. if not the leads last chance will try the coil pack have bucks subaru down the road from me which is handy thaey have loads of good second hand parts and andy is knowledgeable he will be next point of call.