I have a '99 Outback with about 186k that I bought for the kids. My
daughter complained about it running rougher than usual at idle. I
picked it up from her school and she was right! It tripped P0301 and
P0303 codes (misfire on 1 & 3). I was able to limp home with it.
Here's what I have done so far:

1. Changed plugs and wires
2. Changed Coil and Air Cleaner

After doing this, I tried the car. It kept stalling (see detailed description below). I was able (barely by giving it lots of gas) to get it the 20 feet into my garage so I could work on it out of the rain, but that's about it).

3. Changed timing belt, hydraulic tensioner and all idlers (see below, they were past their expiration date)
4. Changed water pump (well, I figured since I was in there anyway...)
5. Changed upper and lower radiator hoses and thermostat (again, since I was there..)
6. Changed alternator/PS belt and AC compressor belt, as well as idler on the AC belt tensioner (after all, my kids are driving it...)

So, here's where the story gets interesting. When I opened the timing belt cover, I found a rubber-covered metal ring floating around in the sprockets. It ends up it is the ball-bearing cover on the idler wheel that has the teeth (don't know the technical term for this). So, clearly that idler was fubar and it's a fair assumption that this foreign body probably caused the timing belt to skip, resulting in the misfires.

I put the car together and started it up. It started right away, sounded smooth, revved up to about 1500 RPM, and then died. Thinking that maybe the computer needed to relearn the idle, I disconnected the battery for a minute or so and then turned the ignition on for a minute or so, and then started it up. Some thing. No CEL and no codes came up, but it just doesn't run.

If I give the car lots of gas, I can keep it running, but it tries to die every few seconds and I need to pump the throttle to keep it running. Don't think that I can move it like this, since every time I try to shift it into gear, it will stall.

Suggestions are welcome!

Thank you.

Make sure the intake tube is fitted properly. The big airbox that clamps to the throttle body can be tricky to get back together properly at the bottom. Check that for proper fitment and make sure it's clamped shut.

Check the large diameter hose from the idle control to the intake tube.

Check the breather hoses that run from the valve covers up to the airbox for proper fit. Also check the PCV hose that attaches to the airbox.

Thank you, Sooberoo.  I tried to remove the big airbox to clean it but couldn't figure out how to remove it.  Any suggestions?

what fairtax said,

there is a large hose that runs from the rear passenger side of the intake manifold to the very BOTTOM of the air plenum pipe .

the air plenum pipe runs from air filter box to the large ''box'' behind the throttle body.

if this is not connected the car will start and then die.

you can keep it running if you goose the gas pedal.

 

check ALL the hoses and vac lines.

a vac leak can cause running issues.

 

there is a possibility that the timing jumped,

and bent valves?

 

but look for a vac leak first.

Thank you, John.  I wil check that out.  ALso, as a Newbie, I didn't see Fairfax' name, but thank  you Fairfax.  I will check out all of your suggestions.

Well, John and Fairfax nailed it.  When I moved the airbox to change the passenger side spark plugs, I must have inadvertently dislodged that hose that John references.  Plugged it in and now, with the new plugs, coil, timing belt and idlers, it runs like a top and MUCH quieter.  I can't thank you guys enough.

you arr welcome for the help,

and

 

welcome to the party,

enjoy.