Seafoamed my 98 Legacy L 2.2 (154k miles) today, running it through the brake booster and another vacuum line on the opposite side of the engine. It smoked, I turned it off for 10 minutes, started it up and took if for a spirited drive, and it ran really well until moments later when the CEL came on, along with a noticable lack of power, too. Took it to Advance Auto so they could scan it, and it's code P0303 for cylinder 3 misfire, and P0325 for the knock sensor (which I already knew about the knock sensor code from several days earlier, and am ordering a new knock sensor). Any ideas on what the Seafoam could've done to cause the P0303? The Cylinder 3 misfire code seems directly related to the Seafoam, what do you think?

Id just clear it and keep an eye on the light. If the CEL starts flashing you have an active misfire and could damage the catalyst.

 

That knock sensor is a huge factor too. When they are bad the car will run like absolute crap at times.

The seafoam shouldn't have caused the misfire. The knock sensor on the other hand can cause a misfire or two. I'd do what ShawnW said and clear the code and if it popes up again, check your plugs when you do the knock sensor. Usually the only dangerous thing about seafoam is that there have been cases were people have hydro-locked their engines putting too much in at once...

Seafoam can very well cause a misfire. I'm surprised that it didn't set it sooner. All the carbon crap being burned off may have fouled the plugs. Reset the code, if it comes back pull the plugs and have a look at them.

I have had plugs fouled by seafoaming through the intake in the past. Hence, now if I do that usually change the plugs afterwards.

how old are the plugs and wires? are they NGK and Subaru wires?

 

personally i wouldn't/don't add the sea foam to the intake. add it to the gas or oil. that being said, i'm a bit doubtful you have anything to worry about. if the sea foam caused it, it will go away and not be any sign of problems, so don't worry about it.

 

typically folks add something when they suspect a problem, so it's also highly probable that folks have something they are hoping the work they are doing helps - poor performance, a slight hesitation, bad gas mileage, etc.

 

i don't know anything about the past maintenance history of this car so i'm hesitant to blame the sea foam on a decade old car with 150,000+ miles running a bit out of tune.

I don't know the age of the plugs and wires, so I'll be ordering those, too. The vacuum lines I'd used to Seafoam were the brake booster (which some say only goes to one cylinder), and the vacuum line to the left of PCV, which is indicated in the picture, and I now realize that it looks like it may only go to cylinder #3? Could that be part of my problem?

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I used a third of the Seafoam bottle as it says to do, and put one half of that third into the brake booster while at the same time putting the other half of the third into the vacuum line indicated in the picture. My wife fed it into the booster while I fed it into the vacuum line. Both were sipped in slowly and simultaneously, took several minutes at least.

The way that I did it, I'm realizing that the Seafoam may not have made it into all four cylinders, correct?

You are right, looks like it didn't make it into all the cylinders. Kind of a benign point though...you could almost argue it's more risky than it is beneficial....

 

When you tear a motor down you will see the cylinders are nearly spotless, you're not "cleaning the cylinders" at all by adding sea foam. I have a 200,000+ mile Subaru engine on a stand right now, the combustion chamber "cylinder" was spotless. Crosshatching from the machining process still visible and chamber spotless.

 

What you are doing is cleaning the intake runners, they get all caked up with black sooty deposits. But it doesn't matter, that stuff isn't hurting anything and it's pushing those contaminants out of the runners into the engine. I would rather it stay in the intake than go in the engine. It isn't hurting anything in the intake runner, they just make it black.

 

Clean oil, frequent oil changes, oil treatments (with seafoam), and fuel treatments are far more functional and helpful.

 

I'd dump the rest of your seafoam in the oil or gas and call it a day.

 

Or ask us what is bothering you or you'd like to accomplish and we'll help you do that.

The vacuum lines I'd used to Seafoam were the brake booster (which some say only goes to one cylinder), and the vacuum line to the left of PCV . . .

 

Feeding the Seafoam in through the PCV hose gives a better distribution. Just make sure the hose is cleared of oily gunk buildup before you do it.

Thanks guys, your wisdom is priceless. The CEL went off literally about 30 minutes ago when I started the car to go for lunch, and the engine was very quiet driving back to work here, very smooth too, but definately still sluggish and now has a split second hesitation when I give it gas. I give it gas and there's a very brief hesitation and then it kicks in. Like the throttle response is delayed, or like it bogs our briefly or something. This problem may be a temporary side effect from the Seafoam and correct itself, I don't know.

 

So suddenly the CEL is off for the meantime, but it was throwing the code for cylinder 3 misfire. Would the CEL turn off if it was still misfiring? The CEL has been going on and off even though I still need the knock sensor, so that's why I'm not sure.

CEL probably isn't related the Seafoam at all and this code will come back.

 

You likely need new plugs or wires (I'd replace both given you don't know history of them).

 

EJ motors are not very forgiving like older Subaru engines which - most of us on here stick with the stock NGK plugs and Subaru wires only.

 

If you're die hard bent on aftermarket wires go with Magnecor, that's what I use.

That's what I'm going to order very soon. Suburapartsforyou.com seems to have everything I'd need; the plugs, wires, and knock sensor. They're all OEM, too (Subaru of America, that is).

 

When I'd gotten the car, I noticed that there was a LOT of dust/dirt covering and stuck all over the engine, and in all the cracks of the vehicle. The air filter wasn't too bad though. Maybe the lady that had it lived up a dirt lane or something. Anything else I should check or clean due to all the dust that my Legacy used to live in?

I personally wouldn't worry about it too much. The internals can be squeaky clean even when the externals are nasty. Many years of dust/dirt/grime and spilled, leaking, dripping oil or grease, cv joints, power steering, brake fluid, etc can give dust something to attach too.

 

Change the air filter and change your oil often and you'll be golden.

Thanks again, I'm meticulous about vehicle maintenance so that'll be no problem at all. I'll post how it turns out as soon as my parts come in!

Update...

 

Installed the new knock sensor (which I got from my local Subaru Steal-ership, who matched on-line pricing which was cool of them). Wow, what a difference already! More power, less hesitation, smoother running.

It was more of a pain to install than I'd expected though, because of such little room to work.

 

The plugs and wires are ready for pick up today, so I'll install them as soon as I can and update further at that point.

good deal. did the CEL go away or stay off now?

 

Wow, what a difference already! More power, less hesitation, smoother running.

looks like my original speculation on the sea foam may not have been entirely inaccurate:

typically folks add something when they suspect a problem,

The CEL is off and has stayed that way since!

 

I'd known the knock sensor was bad and causing some issues, but it had also seemed a little sluggish besides that, which I'd thought was due to carbon build up since a little old lady had owned this vehicle since new before I'd bought it two months ago. She drove it very conservitively, to say the least. The Seafoam treatment had certainly caused it to run better, along with clouds of smoke which made it a lot of fun. So you were right Gary, there were hesitation issues which I was hoping the Seafoam would remedy a little!

 

I'm excited about doing my plugs and wires very soon, too.