2006 Baja. Really rough idle/misfire after parked

[aarockonthedarkside]

Hey guys first post here I think. I'll try to keep from rambling. But will try to give every aspect of detail as it happened. Here we go.

I have a N/A 2006 subaru baja. Bone stock no mods to motor. Currently the 2nd owner. Previous owner stated (cant prove) shop replaced engine at 161k. He dropped it off at dealer and was headed for a road trip they forgot to put oil in it. That said claim it was rebuilt. Currently has about 261k on the clock. I have done a few thing here and there. Fresh fluids mainly. Also rear brake calipers, and front axles-CV joints. I had a few lights out on the gauges so I got some blue leds to replace. Once I tore in to the dash. I plugged one in the cigarette plug turned the lights on and had to flip it (polar bulbs. Hate that) once I confirmed they work I powered ignition off and pulled the neg terminal and continued to finish all the replacements. Had to flip a few again and plugged dash back in with power to ensure they were all on. In between that time when I connected the battery the A/C fans turned on. This has done this before when I pulled the battery. And the alarm went off normal right? On the alarm at least. Well I drove the car all week no issues, and the day before. Here's where the the crazy part starts. I fired the car up to move it a bit. Dash was plugged it and working at that time. Now the car is misfiring exhaust smells extremely bad like raw fuel and billowing smoke. I cant imagine I shorted anything and cant even imagine either are related. Just weird it started after the fact I tore on to the dash. So I thought ok put it all back together and see how it goes. Dash looks great. No check engine light mind you. While I was putting the finishing touches on the dash the door buzzer went off 3 or 4 times then off again never to do it again. Mind you no key in ignition at the time. Started car again after done. And same result. Rough idle blowing fuel out of exhaust and bad misfire. To the point it's almost stalling. Then the idle came back for a min normal them jumped to 3k rpm ran rough again then back down. Then misfires. I pulled a a spark plug or two. Put old ones back in. Thinking just mabey they were bad as I had just installed 2 weeks ago ngk iridium's. Ran great too. The plugs were soaked with fuel. Move on to next day. I bought new ngk plug wires and a coil pack just assuming it would solve issue. Well it didnt. So I pulled it out of the garage. Under it's own power. When I put it in drive it ran fine for a second and then the same idle climbed up started misfiring and so on. I dont know where to start. Fuel pump. Fuel Pressure regulator went out and it just so happed to do it when I parked it the day before. I just pray it's not a computer issue. Thanks for any advice to come. I love this truckcar. Lol. And I dont want to just throw parts at it. Also dont want to give up. Thanks. Sorry for such a long post.

[Shmitty]

I have a very similar problem. Engine misfire, horrible idle, low power. And nothing I do to the poor thing seems to make a difference. I fear the piston rings may have seen better days. I have given it sparkplugs, ignition coils, o2 sensors, the works! And she's still running like a walrus (poorly)
I'm currently in the process of finding out what's wrong. I'll be happy to post my findings as I go. My current game plan is...
Read my codes (for the millionth time) and make sure nothing new has popped up
Do a compression test on all cylinders.
swap out o2 sensor for a OEM one (Mine is currently a generic)

I do have a bit more info about my problem that may help point you in the right direction. My Idle gets ALOT worse (to the point of stalling at stop signs) If I have just disconnected the battery. it will then run like that for a few days and slowly get better, to the point where to do not have to worry about stalling, but it still idles like trash. My assumption is that the ECU "relearns" the idle in a way?

[aarockonthedarkside]

New development. Turns out your right about the relearn part. I had a freind over that just so happened to have his blue point code reader with him. So we hooked it up again. All the same codes. Well his obd2 reader can talk too the ecu. We cleared the codes. Reset everything. Fired car up runs perfect no codes. I've put 89 miles on it since still using old fouled up plugs too. It runs better now than before. Turns out ecu is fine. When I disconnected battery it had a bad ground. My assumption. Not really sure.
That said I did pull off a few grounds cleanes them up. Put back before we touched it. Has a brand new battery it in because the other was getting weak. Well all those codes basically put it in limp mode and never recovered. All senors read fine. O2 and all. So freaking happy right now. Going to run about 200 miles so It can relearn and drop correct stock plugs in. If anything else developes will let you know. As of now car runs solid. I suggest try doing the same. Have a shop if you dont have one reset the ECM.