My 97 Outback at some point before I got it had a 2.0 engine installed in it.  With 260K on the odometer, that's no surprise. What is strange is the following set of circumstances.  

First the car would have one of the cylinder's stop firing from time to time.  If I shut off the engine.. waited a moment then restarted, it would be OK again. So, I replaced the plugs, plug wires and the coil but it persisted.

Then, all of a sudden, it started idling some times fast, sometimes slow and often really missing badly when idling but would run ok once I was driving.  I was sure I was losing a cylinder at this point but went under the hood after about a week of this and was looking at the connection of the coil. It seemed fine but in the process I also was moving around the wires that go from the coil to somewhere I cannot easily see. 

 

When I restarted the car, all of a sudden it no longer misses on idle and the problem with the cylinder dropping out also seems to have disappeared. And the idle has become very consistent at around 500 - 750 rpm when warm. 

 

I can only imagine there is a loose wire somewhere between the coil and where ever it goes and would be a lot more comfortable if I could figure out what is up so I can make sure it doesn't return when I am out on the road.. perhaps even worse.  Any idea on what the issue might have been and what i could do now to make sure this fix becomes solid?

Thanks

What did the plugs look like when you pulled them?

NGK copper core plugs and NGK or Subaru plug wires?

 

It could be a fuel injector.  Plug condition should help you out.

IACV problem (might just need cleaning) could cause idle-only problems.

There are three large plugs on the bellhousing on the passenger side. All of the sensor wiring for the engine passes through those plugs. Ignition, fuel, all of the sensors. If one of those is loose it can cause all sorts of problems. Unplug them, make sure all of the pins are straight and clean, then plug them all back in and make sure they "click" all the way together.

What did the plugs look like when you pulled them?

NGK copper core plugs and NGK or Subaru plug wires?

 

It could be a fuel injector.  Plug condition should help you out.

Had it done and forgot to ask for them back.  Not the sharpest knife in the drawer sometimes.  But, like I said.... now it's running fine. Just can't figure out what I might have done bymoving around the coil wire to fix it.