Rough Idle

[BAC5.2]

I did a search, but came back with nothing. Perhaps someone could point me in the right direction.

I was pulling my car out of the garage this afternoon after working on my interior and noticed something weird.

My idle is real rough.

It stumbles from around 750rpm's to 900 or so. The needle just sort of slowly sways around.

It's solid as a rock under throttle though, I can hold it at 1k without any movement.

Any insight?

Also, there is a weird whine coming from under the hood. It's really faint, so I can't tell if it increases as the revs climb. It's just a whine, that oscilates (independent of the idle bouncing, I don't think it's related. If I stabalize the idle at 1k it still does the oscillation).

Any ideas? Water pump maybe?

How hard of a fix is it if the water pump is going? Driving it from CT to MD, there was no overheating issues or anything. I haven't driven it around on the street yet (bike didn't sell), but it doesn't overheat driving around the neighborhood.

What do you think?

[stant093]

check your vacuum line and try to pin point where the whining sound is coming from. i had roughly the same symptoms and it pointed me to a leaking intake gasket.

[evolutionmovement]

Waterpump's tit. Do the timing belt, too if it isn't new. Usually if the water pump squeaks its because the seals failed and coolant has goten into the bearings. If this is the case it should be leaking coolant from the weep hole. If it does it at idle, try to pinpoint the sound by sticking your head under the hood.

Idle could also be dirty IAC. Mine wobbled for a little while and then idled high when it needed to be cleaned.

How are the filters?

Steve

[BAC5.2]

The filters are new (changed once I got it home and gave it an oil change. Air and oil).

When I started it a little while ago, I didn't hear any whine. Weird. I guess I'll just keep an ear open for the noise.

I'll have all of the belts replaced (including timing belt) when the car goes into the shop to get looked over for inspection.

[ej22t]

Check the injector plugs connection, monsture inside the spark plug wire.

Ben

[vrg3]

The idle problem could be a vacuum leak. I'd first suspect the coffee mug, since you recently installed it and it's the least engineered thing under your hood.

[rB5]

I'm having the exact same idle problem but without the whine (sounds like a separate issue on your car) on my automatic Touring Wagon. Runs pefect until 30-60 seconds (always) after a complete stop then almost stalls with the rough idle. My intake tract is completely stock, but I suspect it's a vacuum leak issue also.

I haven't looked into it yet though, so this was mostly to share the pain than offer up a solution (sorry).

-B

[entirelyturbo]

Now remember guys, these are Subarus. While the boxer action of the pistons is smooth beyond belief above 1500rpm, it can jerk things around at idle. EA82's do it too, as I've noticed, and even a brand-new WRX will do it.

I have never gotten my Legacy to idle perfectly smoothly, and since I'm not going to try anymore, I doubt I ever will. I have replaced my IAC valve, put all new drivetrain mounts on the car, engine is in absolute perfect tune. I can't do anything else.

It's just a boxer engine quirk, one of many quirks that give Subarus personality

[evolutionmovement]

Mine idles so smooth that you can't tell its running to look at the engine. I'm anal about filters and ignition parts, though, and I know the Magnecors made a difference.

Steve

[rB5]

Just thought I'd follow up on this subject for any owners out there with the same symptoms:

My idle finally got so bad that it wouldn't idle on it's own – which was ultimately a good thing! I took it to the shop & it turned out to be a vacuum leak as many theorized before. It was in the intake manifold gasket and started off as a very tiny (undetectable) leak, causing the small annoyance of a rough idle then grew into a gaping leak which created the muscle car-with-lumpy-cams effect. After replacing the gasket my Legacy now idles smoother than my '00 2.5RS!!!

-B