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Old 10-07-2003, 11:11 AM   #1
sybir
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Member#: 4615
Join Date: Mar 2001
Chapter/Region: BAIC
Location: Don of the Wagon Mafia
Vehicle:
05 STi, 97 Leg OB

Default Low/rough idle?

Okie, car has ~150k on it.

Within the last couple days, whether the motor is warm or cold, it's been having a pretty severe vibration at idle, whether in gear or neutral/park (it's a 4EAT). It's idling at about 500-550 rpms, and it feels like there's a load on the motor when I try to rev; give it gas and it still feels like it's got load, but it's not vibrating.

Based on past experience with other cars, I'm thinking spark plugs/wires/rotor/cap.

Any other suggestions or ideas? It does it in and out of gear (obviously worse in gear) so I think it's a motor issue as opposed to a tranny one, and I'm thinking it's not getting clean spark 100% of the time and so is having to push dead cylinders, which is why it's feeling like it's got load on it at idle and vibrating so bad........
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Old 10-07-2003, 12:22 PM   #2
Doug DeRosa
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Location: Madison, WI
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1998 Legacy GT Wagon
Rio Red

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I had similar symptoms with my 98 GT -- rough idle and acceleration, poor gas mileage, but ran okay at speed. It turned out to be the coil, and I was told by the garagae that this is a fairly common problem with Legacies of this vintage.

Pull the plug wires at the coil and see if the terminals at the coil are burnt. If they look fried, suspect the coil. I waited til the "check engine" light came on, and took it in and was basically scalped on the repair. Looks like a real easy job, so I can only hope I might be saving someone else some time and money.
dpd
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Old 10-07-2003, 12:32 PM   #3
sybir
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Default

Ah, thanks. So you're talking the sparkplug wire contacts on the distributor looked burned?

hmmmmmmm
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Old 10-07-2003, 01:01 PM   #4
subster
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Location: Minneapolis, MN
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2008 2000 2.5 RS
1995 SVX

Default No my friend.

Subarus have distributorless ignitions. It's the coil he's talking about on top of the engine, the little black block.
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Old 10-07-2003, 01:24 PM   #5
sybir
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Doh, that's what I meant. Just replaced a coil pack on my friend's car yesterday, so I'm not thinking right
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Old 10-07-2003, 01:42 PM   #6
subster
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1995 SVX

Default I thought so.

I figured you knew better.
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Old 10-07-2003, 02:36 PM   #7
Benjamin Tang
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2009 Forester
red

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i posted something similar a few weeks back:

http://forums.nasioc.com/forums/show...hreadid=429076

could we both be having the same problem, despite having different motors?
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Old 10-09-2003, 12:32 AM   #8
sybir
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Well, ran it bya local Scooby guy, and he went over it with a fine toothed comb before confirming spark plugs

$40, 4 NGK's and a bunch of cuss words (it really sucks to lose your extension between the head and the crossmember ) later, it's runnig like a champ, and revving like it hasn't in a long-ass time

Thanks for the advice; Occam's razor, eh?
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Old 10-09-2003, 09:27 AM   #9
subster
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2008 2000 2.5 RS
1995 SVX

Default That's great!

Good job! You're a real do-it-your-self-er!
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Old 10-09-2003, 10:16 AM   #10
sybir
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Yeah, that or cheap.........


Drove it this morning, it's still there a little bit, but i'll swap out wires tonight, and then the coil.


Word of advice. To switch out spark plugs, use a 5/8 spark plug socket, then a swivel extension, then a 1/2 inch extension. It'll give you just enough length to attach the ratchet, but not so much that you can't get it off again, and it flexes, so you can angle it out. This is an important consideration, given the following.

DO NOT: use a 3 inch extension on the spark plug socket, then attach the ratchet. It'll require ~42 minutes of prying with a screwdriver to detach the component pieces from each other, then you have to fish everything out with a magnet, at which point your socket will roll down in between the heads and the crossmember


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Old 10-09-2003, 10:21 AM   #11
subster
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2008 2000 2.5 RS
1995 SVX

Talking LOL

That's funny! Yeah the ones on the passenger side are easy but the drivers side sucks. You have to take out the windsheild fluid resevoir and the battery. You are going to swap the spark plug wires tonight?
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Old 10-09-2003, 10:58 AM   #12
sybir
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Default

Affirmative, gonna swap 'em out tonight.

I didn't pull the battery, that one was pretty easy to reach, it was the firewall end on the driver's side that was giving me grief with the extensions

I'm gonna swing by the recycler and pick up some wires off a low mileage car to test, and then go from there
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Old 10-09-2003, 11:00 AM   #13
subster
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1995 SVX

Default cool beans.

Is that still cool to say? Oh well, anyways cool man. Have fun!
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Old 10-11-2003, 02:10 PM   #14
Subietonic
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I've had two coil packs go out on the two GTs one under warranty, the other just over the emission control warranty so had to buy it. Both times, the spark plug wire to coil pack terminals were carboned up big time. Suggest replacing your wires at the same time because often the coil is trying to send juice through a wire/wires that have too much resistance (breaking down) and ends up burning itself up trying. You'll also end up with one or more fouled plugs so it's a good idea to at least pull them and clean them, or alternatively if they're worn, replaced.

For what it's worth, I always pull the intake box and the windshield washer box and on the DOHCs the battery before changing out the plugs. It's a ton easier to "turn" and "pull/work" the plug wires loose when you can actually get your hand/fingers on it then it is to try and leverage them off with God knows what jammed down in there between all that stuff and the valve cover. Plus, it's a simple, straight in shot with a 5/8" plug socket and you can actually bend over and "see" in there if you need or want to. Adds about 5 minutes per side to take the stuff out and adds years to the environment because you're not replacing all the air around you with cussing and swearing blue smoke. Just my .02 worth.

Three other things that you'll want to look at/check is the idle air control valve, the throttle body and the grounding mod. I've done a pretty straight forward, detailed writeup on all of these if you just do a search on my screen name.

Br, Dale
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Old 10-11-2003, 02:40 PM   #15
sybir
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Join Date: Mar 2001
Chapter/Region: BAIC
Location: Don of the Wagon Mafia
Vehicle:
05 STi, 97 Leg OB

Default

I'll check out the IAC, searching now. The plugs I pulled were clean, just worn (ie big gaps). The terminals, from what I can see, look brand new, but that's just from what I can see, so who knows.

One of my thoughts was the IAC, but I didn't know how to screw with it; the rough idle goes away if I even breathe on the throttle, so it's a possibility.

Thanks for the advice. What, in your opinion, would I be looking for in the throttle body?
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Old 10-11-2003, 02:55 PM   #16
Subietonic
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Default

Sybir,

Here's the Throttle Body post. It gives you a pretty good idea of what to look for.

The Idle Air Control Solenoid writeup is in that same post as above, just further down in the threads.

HTH.

Br, Dale
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Old 10-11-2003, 10:11 PM   #17
atabert
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1992 Legacy L
Green

Default rough idle

you could also have a faulty injector somewhere
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