nastylgt

Problem solved! I KNEW I did everything right. Everything besides the the old intake manifold gaskets off. The driverside gasket was still on. And actually had fallen off and I didn't notice it. It got sandwiched halfway over the manifold ports. Causing a major exhaust/vacuum leak. Removed it and it runs like a dream. Thank you everyone for advice and tips!

Nope. That didn't work either...

Nope. The CEL light doesn't even come on.

I've gone through the top of the intake and air box. I know what hose you're talking about. Its connected...

Okay so I recently replaced the head gaskets and timing belt kit on my 1999 Subaru Legacy SUS 2.5 DOHC. Got the motor back in yesterday and went to start her and it didn't want to stay running. Would have an extremely rough idle right after start up and die after about 3 or 4 seconds. If you feathered/smashed the gas pedal, it would stay running but it sounded terrible. I've done a little bit of research but can't really find any good info on what it may be. Timing belt is 100% correct. All marks on cams were aligned and the crankshaft gear notch was lined up with the notch on the block at top dead center. All marks on belt lined up with the notches on the cam gears and timing cover. All wiring, connectors, and grounds are good....gonna go over the motor again today to double check everything. The only things I could think of it being are: Bad sparkplugs/wires. (They looked fine but they were the plugs that were in prior to pulling the motor. Along with the wires. But I thought I read something about getting new Plugs after the heads have been machined...something to do with the compression?) Plugs are NGK iridium. Fuel lines are ran right and tightened down. No gas leaks or smells. Did a compression test today. All cylinders read 200-210psi. I'm losing my mind! I've attached a few videos... https://youtu.be/xpoOO2hx-YY https://youtu.be/xPJKI4hTiTY https://youtu.be/PEsRfJ8Ihqw

Also, does anyone have any tips for a good safe cleaning agent to be used on the block?

CEL is still there. Haven't gone to get it read. Almost 100% sure it'll say both, knock sensor and o2 sensor. But the thing is, when I disconnect the knock sensor and the battery for about 15 minutes, and connect everything together, the CEL goes away and the car drives fine. But only for about 4 days. Then it returns and the car is extremely sluggish while accelerating and rough in between shifts. Doesn't this mean something is wrong? Lol I don't want to buy a new knock sensor if this one is still good. I've cleaned the block surface (somewhat dirty, can't get all of the corrosion off, but still pretty smooth) and the knock sensor (hardly dirty at all) at least 3 times now. If it's possibly in the wiring/harness, THEN what do I do? Any input appreciated.

This time, they told me "bank 1 sensor 2"...which makes me think ita the downstream but the downstream is literally brand new. And ill have to clean the mating area and see if that helps. Thanks

Bought the car with 186k miles. Cel read knock sensor and o2 sensor. Replaced the knock and the rear o2 sensor. CEL went off for about a week then returned. Took it back to AutoZone and it read knock sensor and o2 sensor again. Will replace upstream o2 sensor this time but what's up with the knock sensor going bad again? Could something else be causing this?