misfiring
Asked by garyforester2004 Jun 15, 2018 at 07:46 PM about the 2004 Subaru Forester X
Question type: Maintenance & Repair
I have recently purchased a 2004 Subaru Forester. It's running really rough.
Engine shaking like it's misfiring. I pulled the spark plugs and found (I
believe) the 2 and 4 cylinders are not firing. I replace with new spark plugs,
and it's still running rough. I replaced the wires and still running rough. The
spark plugs are getting spark, but when I pulled them out to a compression
check (all cylinder have very good compression), I noticed two of the spark
plugs looked like they came right from the box and the other two looked like
they have been firing.... What could course this?
16 Answers
You may want to replace the coil pack. If the spark plug tubes are full of oil you may want to replace seals.
garyforester2004 answered 6 years ago
I replaced the coil and no difference.
Are the plug wires mixed up?
I would verify that the plug wires are actually on correctly and listen for arcing. If a plug wire arcs to ground the engine will miss.
garyforester2004 answered 6 years ago
Thanks F_O_R, I'll check for that.
TheSubaruGuruBoston answered 6 years ago
The motor will not run if BOTH cylinders on one side aren't firing. Misfiring will always trigger CELs, notably PO30x, x=# of cylinder. If you're SURE you're getting ignition AND fuel, then there's a decent chance you have an (internal) valve issue issue, which isn't worth fixing, given the vehicle's age.
According to the original post the engine has good compression on all cylinders but did not say how many psi that is.
I would check to see if all the fuel injectors are working as they should be.
HOWZIT GARYFORESTOR2004. Did you manage to sort out the issue with your subaru forestor?
Brandon2008forester answered 4 years ago
Dealing with this same problem any advice on how you fixed it?
Got no answers but I got problems, head gaskets leak, valve adjustments ,replaced wires,plugs, flinge on cat,conv, Diagnosis ,several times still misfiring,shaking and engine check light solid, 2003 Subaru Forester, any comments!?
TheSubaruGuruBoston answered 4 years ago
Swap your ignition coil out for a good one if you have a chronic misfire, as they crack from age. If still missing, AND you're sure the new wires and plugs are well-connected, AND the misfire is only one cylinder, then the odds are you need valve work. Not worth it on a dinosaur this ancient. Sorry. Ern TSG/B You mentioned valve "adjustments". What are you referring to? To sometimes see a hung- up valve guide you can drop the exhaust and look up from the bottom and see the protruded guide. Regardless, PITA for such an old carcass....
Its the crank position sensor. It about to go out completely.
