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2005 Legacy GT
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Discussion Starter #1 (Edited)
I'm not sure if the idle is surging or dropping. Once the car is warm and the idle is a little erratic. It bounces between 500 - 1k RPMs, just goes back and forth. The weird thing is that this bounciness is not consistent it will do it most of the time, but sometimes the idle is just fine (around 600 - 800).

I have checked the IACV it is ok and functioning properly.

I've replaced the fuel filter and run some injector cleaner through the engine.

Could this be a vacuum leak?
Also I think I might be running a bit rich (I can smell fuel when it's in my garage ... garage door is open ... I'm not quite that dumb) ... could this be the result of said hypothetical vacuum leak?

Could the (potentially) unburned fuel be the result of the fuel having to high of an octane rating (I really doubt this, but I think it's good to cover my bases)?

I have not checked the FITV yet (f***in' fuel line is in the way and I can't get a screwdriver on the damn thing). This may be a good next step ... but the last time I had a problem with this it was a really start up, but was fine once the engine was warm.

Also I have a b7/z6 mini-me ... running on a z6 cam gear. I understand that this is the wrong cam gear to use and either this weekend or the next I plan on remedying that issue ... what are the chances that this will fix my problem?

Just trying to narrow things down before I start "fixing" the problem.
 

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2005 Legacy GT
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Discussion Starter #3
Def a vacuum leak
Well that narrows it down ... a bit.


So the best way to fix that is ... buy a bunch of vacuum hose and start replacing lines? I think the IM gasket is new ... I'll have to check on that since I didn't do the head swap.

Other likely places? I'm going to pick up a can of carb cleaner today and check it out.
 

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Well that narrows it down ... a bit.


So the best way to fix that is ... buy a bunch of vacuum hose and start replacing lines? I think the IM gasket is new ... I'll have to check on that since I didn't do the head swap.

Other likely places? I'm going to pick up a can of carb cleaner today and check it out.
Test TB, IM and general hoses.

Also, how old is your map sensor? Is your tune good?
 

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2005 Legacy GT
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Discussion Starter #5
Test TB, IM and general hoses.

Also, how old is your map sensor? Is your tune good?
Map sensor ... I don't know. At least two years of sitting in a garage + the ~60k miles that were on the head when I bought it.

Tune ... just running a stock z6 base map from a virgin p28.

Maybe I needs to get new MAP sensor?
 

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2005 Legacy GT
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Discussion Starter #9
Ok back from work ... and I have another question.

I've never done this before so please bear with my silly questions.

When checking for a vacuum leak should I let the engine cool down before spraying carb cleaner all over the place (I would really rather not have anything catch on fire)? And is there anywhere I should avoid spraying it (again I'd rather nothing went up in flames)?
 

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Ok back from work ... and I have another question.

I've never done this before so please bear with my silly questions.

When checking for a vacuum leak should I let the engine cool down before spraying carb cleaner all over the place (I would really rather not have anything catch on fire)? And is there anywhere I should avoid spraying it (again I'd rather nothing went up in flames)?
Avoid spraying on Exhaust header and Alternator.

Let your car stableize it's idle first.
 

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2005 Legacy GT
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Discussion Starter #11
Well I did that and the carb cleaner didn't appear to affect the idle. It'd be fairly dramatic and noticeable if it did right?

Sprayed it around gasket mating surfaces, and what vacuum hoses I could identify.

It did however give me a bit of a headache.

Maybe I should let it warm up a bit more? Idle doesn't really stabilize.
 

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I survived code 9
1998 Honda Civic DX
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1,662 Posts
I wouldn't use carb cleaner to check for vacuum leaks.

Use like a propane torch without the flame. Just look for inconstancy in idle at a certain area when it "picks" up the propane.

I'm not responsible if you blow yourself up.
 

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2005 Legacy GT
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Discussion Starter #14
I wouldn't use carb cleaner to check for vacuum leaks.

Use like a propane torch without the flame. Just look for inconstancy in idle at a certain area when it "picks" up the propane.

I'm not responsible if you blow yourself up.
Every DIY I've read so far suggests either carb cleaner or propane. Not having a readily available source of propane ... I have to go with carb cleaner.
 

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2005 Legacy GT
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Discussion Starter #15
Update ... slowly eliminating problem areas.

Pulled IACV off an cleaned it ... just in case. Still having erratic idle.

Messed with ignition timing. Still nothing, changed the speed, but still bounced, just at a higher or lower RPM.

Pretty sure I'm running rich ... grayish smoke from tail pipe.
It also looks like I've got a bit of condensation back there, what could that be?

And after putting IACV back on ... getting a whistle from TB/Intake. I think it was there before but it's more pronounced now.


May just have to bite the bullet and take it in.
 

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2005 Legacy GT
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Discussion Starter #17 (Edited)
Whistle IS your vacuum leak

Fix it.
Sounds like it's coming from inside the throttle body ... new TB gasket needed?


Also it's kind of odd that it got worse after taking the IACV off, cleaning it, and putting it back on (at least it appears to have). Needs to get me some liquid gasket for around that thing?

Appears to be coming from the hole in the TB that leads to the IACV. Bah maybe I needs to just pull everything off.
 

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Leave the IACV without liquid gasket though you may want to replace the O rings.

And yes a new TB gasket would be good. MAKE SURE you clean both surfaces perfectly.
 

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2005 Legacy GT
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Discussion Starter #19
Pulled TB and what not. FITV was loose tightened that up. Haven't gotten everything back together yet. The "8" ring thing on the IACV looks good to me, I would need to go to a dealership for that wouldn't I? TB gasket looks to be in good shape, but I suppose a new one couldn't hurt. Time to put everything back together and see what happens.
 

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Pulled TB and what not. FITV was loose tightened that up. Haven't gotten everything back together yet. The "8" ring thing on the IACV looks good to me, I would need to go to a dealership for that wouldn't I? TB gasket looks to be in good shape, but I suppose a new one couldn't hurt. Time to put everything back together and see what happens.
Sounds like a plan. If that doesn't work out, just replace both since I recommend you go to the dealer for either one.
 
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