Rough idling after a seat swap

[T268]

Hi all. First post. Thanks for having me. I have an 06 legacy 2.5i. 110k miles. Once or twice in the last 2 months I’ve noticed a little rumble from the engine/transmission if I throw it from reverse to drive quickly and hit the gas. The issue was mitigated by just giving it a second between switches.

 

Fast forward to last week. For a while our power seat wasn’t working. I had it checked out at my mechanic(a AAA certified shop although not a Subaru specialist). They found a donor seat with the motor I needed and gave me the option of buying it rather than spending more from the dealer for new parts. Done and done. Seat works great. I drive away and the idling is rough, but I just assume that’s because the battery had been disconnected during the work. As I drove it got better. The next morning, rough idle again. I throw it in reverse, switch to drive. I didn’t get more than a mile when I stepped on the gas the engine felt out of sync/ shuttering and a flashing check engine light came on. I stopped, let the idle smooth out and the CE light went off. I brought it back to the shop and they said that all the electrical connections look ok, but the read the code for me and it was a misfire at one of the cylinders. They opened it up and said the valve cover gasket at the cylinder the code indicated had gone bad. They cleaned it up, said it needed to be replaced but not necessarily right away. They did recommend new spark plugs and a tune up once it gets done.

 

I trust these guys. They could have screwed me over a dozen times in the past and they never have. They didn’t charge me for this visit either. However, it still seems fishy that this problem of the little rumble has been magnified to a factor of 10 after they worked on it. I wonder if they’re missing something. Anyone have any thoughts?

 

Thanks for the insight.

 

Drew

[SageAbkatsor]

I wonder if they meant the spark plug tube seal? The valve cover gasket covers two cylinders. There is a tube seal for each cylinder. Maybe the tube seal is leaking? If they took the valve cover off they should have replaced the valve cover gasket and both tube seals...

 

What I suspect happened is that they simply pulled the plug and found oil in the tube, indicating the tube seal is leaking. This will foul the plug and can cause misfires. If this is what is happening then do not wait. These cars do not like misfires and they can cause other issues. This is a relatively simple repair, as long as they do not also have to do the half moon cam plugs on the back of the cyl heads as well. Have them put spark plugs in at the same time.

 

I don't think that any of this has to do with the seat repair. You touched on it and I agree that the problem may have been exacerbated by them disconnecting the battery, but if you have oil leaking into your tube seal that is the other reason it is progressing. There is more and more oil in there as time passes by and the plug gets more and more fouled.

 

The first thing that you should do, and probably even do this yourself, is clean the Mass Air Flow meter sensor at the air box. Go buy some MAF cleaner and a screw driver and it will take you 5 mins. Second thing you do is get more information from your shop. If the tube seal is leaking and causing a misfire, I would have that fixed.

 

My .02

 

EDIT: I thought you had a turbo car, but I just re-read your post. Yeah it is probably not as urgent in that case, but still a very easy repair, and that is likely what is happening. If you are actively misfiring then you need to have it fixed before it takes out your catalytic converter. You could still clean the MAF, but I have definitely seen those tube seals leak before and cause plug fouling. If I were a betting man then I would bet that is what the shop found. An added bonus is that the job is even easier on your engine, and there are no half moons to reseal regardless.

Edited July 30, 2019 by SageAbkatsor

[T268]

Yeah, non-turbo. I haven’t got the misfire feel or check engine light since the one time I’ve described. Just hard idle each time I start up and after about 1-2 minutes, things settle down.

 

I really appreciate your insight. They must have been talking about the tube seal as they were talking as if the seal in question addressed one cylinder(at least I think that’s what I heard). Thank you! I’m glad to know that they’re thinking along the right lines, and that the repair they suggest will hopefully address the issue.

[moral hazard]

You can't replace one tube seal on its own.

 

To remove the tube seal, you need to remove the valve cover , at this stage any mechanic would replace 2x tube seals and the valve cover gasket in one go. Cause you're paying mostly for the labour of removing the valve cover, the gaskets/seals are cheap. You never just replace one on its own.

[SageAbkatsor]

You can't replace one tube seal on its own.

 

To remove the tube seal, you need to remove the valve cover , at this stage any mechanic would replace 2x tube seals and the valve cover gasket in one go. Cause you're paying mostly for the labour of removing the valve cover, the gaskets/seals are cheap. You never just replace one on its own.

 

Who suggested this? He just said the mechanics were talking about a seal that failed for one cylinder, not that they would replace just one tube seal.