'90 Legacy. Due to some idle issues and 150K on the Odo, I decided to do a Seafoam treatment. I used the PVC inlet and put 1/3rd thru the intake, 1/3rd in the crankcase, and 1/3rd in the tank. There was 1/4 tank of gas left when I put in the Seafoam, but I filled it the next day.

 

It ran rough even after the exhaust ran clean - acted like ony 2 - 3 cylinders were firing. Took it for a short drive and smoothed out - back to 'normal'.

 

The next day started up and ran rough for the 1st 2 minutes, but then smoothed out again by the time I got to work (~5 min. commute).

 

I changed all 4 plugs that night in case one got fouled.

 

Next day ran fine but I went over a speed bump a little fast and the car ran rough for a few seconds, but smoothed out.

 

This a.m. the car started to run rough again after a couple minutes of commuting....never did smooth out b4 I got to work.

 

Any ideas?

When was the last time that the spark plug wires were changed? Also, maybe the PCV valve needs to be replaced? Maybe, the fuel filter needs to be replaced? These are thoughs that come to my mind.

 

I have used Seafoam, and have been happy with the results. It does a good job of cleaning away engine deposits. Only negative that I have ever heard about Seafoam is that it is hard on engine seals and gaskets.

When was the last time that the spark plug wires were changed? Also, maybe the PCV valve needs to be replaced? Maybe, the fuel filter needs to be replaced? These are thoughs that come to my mind.

 

All those items are about a year old.

 

I've read more online and I'll just give it another few days to 'work thru the system'. (I hope!)

 

Thanks

Maybe a stupid question, but did you change the oil after putting it in the crankcase?

Maybe a stupid question, but did you change the oil after putting it in the crankcase?

 

Nope...did I miss something? I thought it was like an 'oil treatment'.

 

The instructions HERE don't mention doing an oil change.....so I figured I'd wait 'til my next LOF.

Next day ran fine but I went over a speed bump a little fast and the car ran rough for a few seconds, but smoothed out.

 

Any ideas?

 

I'd look for a loose or worn electrical connection.

I actually use it everywhere BUT in the crankcase. Ive heard too many horror stories about broken seals. The shaking and shuddering you are talking about and then smoothing out sounds like my 96 outback with 175k on it. I only put it in the PCV inlet and the gas tank and it smoothed out. If that doesnt work then you might have a corroded gasket. Is there any CEL?

I'd look for a loose or worn electrical connection.

You might also check your plug wires and/or put some Die Electric Grease on the ends.

Yes, I did read where it might be hard on seals, even though I put in less than 5 oz. of the stuff..might just change the oil

 

No CELs...but this is OBDI, so it may not be as 'sensitive' as the OBDIIs?

 

 

Thanks

Nope...did I miss something? I thought it was like an 'oil treatment'.

 

The instructions HERE don't mention doing an oil change.....so I figured I'd wait 'til my next LOF.

 

I'm not sure you can call it a true lubricant. Most of the folks I've seen who put it in their crankcase change the oil after driving for a few miles max.

 

I personally would rather do a few short term hot oil changes rather than put a solvent in the crankcase.

 

Thinking about it more, you could have flaked off a piece of carbon from your intake manifold that may be messing with a valve.

'90 Legacy. Due to some idle issues and 150K on the Odo, I decided to do a Seafoam treatment. I used the PVC inlet and put 1/3rd thru the intake, 1/3rd in the crankcase, and 1/3rd in the tank. There was 1/4 tank of gas left when I put in the Seafoam, but I filled it the next day.

 

It ran rough even after the exhaust ran clean - acted like ony 2 - 3 cylinders were firing. Took it for a short drive and smoothed out - back to 'normal'.

 

The next day started up and ran rough for the 1st 2 minutes, but then smoothed out again by the time I got to work (~5 min. commute).

 

I changed all 4 plugs that night in case one got fouled.

 

Next day ran fine but I went over a speed bump a little fast and the car ran rough for a few seconds, but smoothed out.

 

This a.m. the car started to run rough again after a couple minutes of commuting....never did smooth out b4 I got to work.

 

Any ideas?

 

 

ideas, yes. you did it wrong. sorry, but the interweb has a lot more info on seafoam than just on the back of the can. CHANGE YOUR OIL NOW or better yet, go back in time, add seafoam to the warm crankcase and idle for a few minutes and then change your oil. Seafoam will only rule out mystery engine operation caused only by carbon build up but won't fix and may just reveal other more serious problems. have you ever put a gas treatment in your tank with 1/4 tank and run the engine? why would you do it with seafoam?

 

it works in carpentry as well as auto maintenance: measure twice and cut once. I'm afraid you didn't even put out the tape measure

 

Finally, doing this on a 150K subie (for the first time?) may require more than one treatment in small amounts of ~5 oz before you see benefits. good luck.

I'm afraid you didn't even put out the tape measure

 

Wow, tough crowd!:-\

 

Hmmm, I read the can, read many posts here and elsewhere online (albeit most were about the intake; not the crankcase). Not sure what else I woulda/coulda/shoulda done....other than leave well enough alone.

 

I'll get that oil changed, b4 I incur any more wrath.

 

The good news is that the car has ran fine the last 2 days. Unfortunately the slight idle problem persists....but that'll hopefully be rectified w/a 'little' swap I have planned.

 

 

Thanks again for the input. USMB Rocks!

Well no CEL might mean the OBD 1 isn't as sensitive as 2 I agree. Any puddles of oil at the stoplight or parking space? Or does the oil on your dipstick have a "milkshake" look to it or look funny at all? I know that seafoam hits the head gasket and oil pan gasket the hardest. changing the oil pan gasket isn't so bad but changing a head gasket in a DIY setting is a pain even for those who have done it before. Look for oil loss first before jumping to any conclusions.