I just bought a 2002 forester S with 200k.  Drives ok, but at idle the motor is shaking a little and the exhaust is sputtering.  I ran the codes and they were initially po301, po302, po420 and po442.  Previous owner couldn't pass emissions he says and gave up on her.

 

I cleared and drove it some more and got back a pending po301 and a po302 and that is it.

 

I was thinking of switching the wires from side to side and putting on a spare coil I have to start.  I figure it could be injectors or valves after that.  Anyone else have an opinion?

 

 

Sounds like a good plan.

I'd also look at the plugs - copper core NGK and Subaru or NGK wires as you know.

 

Fuel Filter/fuel pressure check.

 

Good Luck,

look for oil on the wire boots

 

1&2 share a coil so, coil pack is a good idea

Cylinders 1 and 2 share the wasted spark coil, so a coil, terminal, wire, or plug problem could affect both cylinders. Usually this means the coil pack is the issue but it could be coincidence. If a spare coil doesn't solve it, then run a compression test across all 4. If 1 and 2 come up low then the problem is internal because they don't share a camshaft so timing is ruled out. In that case most likely would be burnt exhaust valves which will be a re-ring and new valve situation.

 

GD

so I swapped a working coil and 2 known good wires and same behavior.  I am going to pull the plugs on that side next but my gut is telling me it is the exhaust valves.  there was a little bit of oil on the plug wire of #3, but not dripping.

Edited September 14, 20178 yr by 3Pin

put in new plugs and replaced the knock sensor after getting a code for it.  Still getting misfire in 1 and 3.  I also put in some premium fuel and some fuel injector cleaner as a last ditch.  Seems to run better than it did before, but still is send me a pending code and eventual code for miss on 1 and 3.

Edited September 15, 20178 yr by 3Pin

Try swapping inspector.

Try swapping inspector.

You mean the ignitor? It's built into the coil pack so he already did.

 

GD

Did you mean to say fuel injectors on 1 and 3?

Edited September 15, 20178 yr by 3Pin

Fuel injector. Stupid auto correct.

 

Yeah. I mean if you seriously think you noticed a difference after putting cleaner in...

I don't know. Worth a shot.

Edited September 15, 20178 yr by golucky66

It's faster to do a compression test as the next test. But injectors may be indicated if it's got good comp. numbers.

 

GD

I think I will drive it tomorrow for a bit and see.

It's faster to do a compression test as the next test. But injectors may be indicated if it's got good comp. numbers.

 

GD

Provided he has, or has access to a tester. Yeah that would be a lot quicker as the next step. Completely forgot about compression testing in this scenario.

 

Love being able to turn around, open my toolbox, and have everything i need right there.

Edited September 15, 20178 yr by golucky66

Well I usually have to walk over to the diagnostic tool shelf for the compression tester. It's a little farther than turning around to my box. I keep that stuff more centrally located so all the guys know where to find it. Expensive diag tools are community use at my shop. I don't expect the techs to buy that stuff.

 

GD

Oh man. I wish my shop was that nice.

I agree.  Compression test next.  To the shop for that.

yup, exhaust valves.   Well, engine is coming out to fix the valves and the rear main is leaking and HG are starting to seep.