I drive a 1998 Forester I've had it throw codes quite a few times now.  First time, a month ago, there was a lot of lurching, it was repeated misfires.  Got sparkplugs changed (went with NGKs) and new plug wires as well.  Ran nicely after. I had it diagnosed at an autozone, so while I think it was 3 and 4 misfiring, I didn't get a look at the exact diagnosis so I'm not 100% sure.

 

Second time, used my OBD II reader, 3 & 4 misfires.  Had them pretty consistently, swapped the coil pack.  They seemed to stop. 

 

The engine threw the same cylinder 3 and 4 misfire codes on the way home today.  I've heard from friends that injectors seem unlikely since the misfires wouldn't be this random if that were the issue. Not all that sure where to go next.  MAP sensor or vacuum leak?

 

Possibly irrelevant facts:

1. Swapped my clockspring last night.  Successful. Airbag light is off and horn and cruise work again.

2. Driving (or trying to drive) from Ogden, Utah to Oshkosh, Wisconsin in 3 days. Joy.

plug wires are the most common cause of mis-fire codes.

 

since your codes seem to be 3 & 4,

it is highly likely that it is either the coil or the igniter.

and since you have replaced the coil,

i suggest you replace the igniter.

^^^^ good post

 

can you swap the wires to cyls 1 & 2 ?

 

what brand wires are they?

And to play 'devi's advocate', it's not uncommon to see crispy (burnt) valves on these engines....EJ25D.

 

I'm not a mech, but the fact that your fixes are temporary tells me that something is causing the parts you replace to fail again.

 

This car has a MAF - not a MAP - and they are readily avl. used. Every non-turbo Impreza and Legacy from '92-'98/'99 used the same Green label MAF....but that doesn't explain the 3 and 4 only misfire.

 

BUT go grab the Igniter / ignitor - they're also interchangeable w/the cars above ( I think - unless it's integrated w/the coil?) - and hopefully you can get to WI w/out issue.

 

Td