Seafoam in Brake Booster(P0304)

I was just browsing NASIOC and noticed somewhere it states that the reason people dont seafoam through the brake booster sometimes is because it runs to Cyl 4 so you mostly only clean that cylinder if you run it off the brake booster. So i am wondering, for SURE cleaning of my cylinder and valves wouldnt it be a smart idea to pour some seafoam through that line?

Things I got/did after P0304:

MSD Coil

NGK Plugs

New Wires

New front o2

CAI

UEL Headers

Stromung mid pipe w/ cherry bomb

Apexi WS2 catback

Swapped Injectors

Swapped Injector Plugs

i did 1/3 through pcv also by the way, and i also ran a whole tank with a whole bottle of seafoam (poured it in empty tank, then filled whole tank with some gas.)

I also have deep creep(seafoam for intakes in aerosol form) and about 2/3 of a can of seafoam left.

plugs were before seafoaming, but honestly car barely smoked when I seafoamed through the pcv valve. I also changed fuel filter before seafoaming. Plugs were changed BEFORE seafoaming also. I honestly did not think I would even have to seafoam it, until all of those parts being changed did nothing(upgraded as I troubleshooted of course.)

Reason being i want to seafoam most of the 4th cylinder is because if its the valve the seafoam could brake it loose or clean of some gunk off it.

About 2k miles ago I did headgaskets, in which i RESEATED all of the valves, resurfaced heads, and replaced every single valve stem seal and properly seated it. I highly doubt it could be the valves, but I dont even know anymore.

Timing shouldnt be off, and if it is wouldnt it be setting off P0304 and P0302?

 

Things I got/did after P0304:

MSD Coil

NGK Plugs

New Wires

New front o2

CAI

UEL Headers

Stromung mid pipe w/ cherry bomb

Apexi WS2 catback

Swapped Injectors

Swapped Injector Plugs

1/3 SF in tank.

1/3 SF in crankcase.

1/3 SF in brake booster.

Btw, when you added all of those small upgrades & Seafoamed the engine, did you reset the ECU? If not, now would be the ideal time to do so.

yeah i reset the ecu after i did the last upgrade(exhaust) i did not reset ecu after seafoam because i dont think thats needed. I also do not want to run any seafoam through the crank so none of my seals decide to go.

Im at 128k miles.

If you have a MAF it shall be cleaned.

Check the valve clearance too. If the clearance is too tight the valves may not close completely and cause misfire and possibly also valve damage. A compression test may reveal valve damage but not too tight valve clearance.

Of course - if you have an engine with hydraulic lifters (I can't remember which engines that has and has not as usual) then the valve clearance shouldn't be an issue unless you have a completely frozen lifter.

Now I'm not sure but do you have a central coil pack or individual coils for each cylinder?

If there is a central coil pack you may replace the ignition cables. One of them may have been damaged and the spark is jumping somewhere to ground.

i did not reset ecu after seafoam because i dont think thats needed.

Your ECU may have adjusted to the pre-ignition that was probably happening when the built up carbon was still there. I just may be paranoid but I've always reset the ecu after I've cleaned or replaced a mass of parts just to see how the car responds.

Side Note: Check the wiring around Cyl#4 & see if there are no open areas that can cause a code.

I've got an 04 N/A Legacy. Was planning to change my oil this weekend, wanted to SeaFoam as well. Last time a friend helped me suck about 1/3 of the can through the brake booster (circular protrusion from the firewall, drivers side). I've got a VERY rough idle, the car shakes a lot. Could be revving a bit smoother as well.

Where should I actually suck it in? Could someone provide a picture (><). Thanks!

I've got an 04 N/A Legacy. Was planning to change my oil this weekend, wanted to SeaFoam as well. Last time a friend helped me suck about 1/3 of the can through the brake booster (circular protrusion from the firewall, drivers side). I've got a VERY rough idle, the car shakes a lot. Could be revving a bit smoother as well.

 

Where should I actually suck it in? Could someone provide a picture (><). Thanks!

1/3 in brake booster line.

1/3 in crankcase.

1/3 in gas tank.

When you see thick smoke coming out of the tailpipe & the engine starts the sputter/slow down, rev the s**t out of it. I'm talking like near-red line status. Your engine needs to be spinning at high rpms for the Seafoam to do it's job properly. Rev it high for about 10-15 seconds, & then back off & let it idle for 30 seconds, then repeat until the thick white smoke disappears (there WILL be a LOT of smoke so make sure you're away from people or they'll get panicked & call the cops). Then change your oil again & fill your gas tank up to clear the lines/engine.

Sorry I'm a little car-dumb. Brake booster is the line that's on the firewall essentially in front of the driver and crankcase is the oil? or is that the PCV hose others are mentioning

PCV hose. You can also put it in the oil as well but I always use the PCV hose.

ive tried to swap wires, and i have a single coil pack(which the MSD replaced the old one.) Car doesn't run all that great honestly, idle is shaky and it feels like its misfiring. Usually worse when reallllllly cold out(so everyday haha.)

Mechanic i talk with all the time(subaru guy) hes been a mechanic for years, my neighbor used to go to him in the 70's! Anyway he said that i should just drive it until it dissapears, but that isnt really logical for me. Should i swap the ecu? What ecu's would work for me?

gonna do oil change, fix ALL of the exhaust leaks because the exhaust mani was slightly leaking during seafoam.

Car doesn't run all that great honestly, idle is shaky and it feels like its misfiring.

 

Should i swap the ecu? What ecu's would work for me?

Did you rev it to high rpms when the Seafoam was fully poured in? If your exhaust is still smoking white, then there is still Seafoam left.

Outback ECUs will work for you. Direct plug-ins from 96-99. Don't use L ECUs (Ls). They're for EJ22s & may make your EJ25 run lean. They'll also lower your max rpm limit by a few hundred.