Nightmare Diagnosis - idle would pulse from 500 to 2000rpm 2-3 times then stall
 

Symptoms: After winter storage Reinstalled battery, drove car for around ¼ tank of gas, parked for the night, in the morning drove to work without issue. When leaving work car idled rough and had no power, put on 4 way flashers and made it home (work is a 10 min drive from home). Check engine light (CEL) did come on during drive home.

ECU scan came back with PO50A* error. Cleared error. Tried starting car, it would start, but idle would pulse from 500 to 2000rpm 2-3 times then stall. No other CEL.

Solution
Primary Issue: Faulty Mass Air Flow (running rich unspent fuel ran into catalytic converters)

Secondary Issue: Catalytic Converters Melted which plugged exhaust

*Error Code P050A is defined as Cold Start Idle Air Control System Performance.

...yikes. That sounds like zero fun.

Are you able to hook the car up to a battery tender when you store it so that you don't have to remove the battery from the car? Did you put any fuel stabilizer in the tank when you stored it?

Are your primary and secondary issues confirmed or theoretical?

mouse house in the exhaust?

yeah we did put fuel stabilizer in..the car was stored to far from power and on a farm.

They guys at Touge tuning/Guelph Subaru confirmed this

second thing I thought of after bad gas(we siphon the gas out also)... There was a mouse nest (suspect shrew bc no wire damage) under the intake too furthering the confusion. Touge Tuning traced all the wiring harness with no evidence of chewed wires. That wasn't cheap.

And potentially the air box. Wouldn't be the first.

MAF Spec is 2.21-2.69 kohms - Tested at 1.9 kohms

Here is the exhaust

what is it? i mean, i understand it's plugged, but with what?

It's the front pipe, with the second Catalytic converter. The first Catalytic converter carbon melted into the second, ruined the over pipe. Replaced it with a Tomei header and invidia overpipe and high flow catalytic converter front pipe. it now has that subie purr

fortunately it has a Jackson racing supercharger system which has a modified air intake and cone air filter

so a mouse house wasn't all that far off ;)

Well that sure ain't pretty!