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Old 11-18-2012, 12:24 AM   #1 (permalink)
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Default Found vacuum leak, now car dies

I finally traced down the hissing sound hear my throttle body/ y-pipe.

Turns out it is the brake booster line that had a big cut in it? It's the 6 inch brake booster hose behind the y-pipe, I replaced with a new one.

My idle use to be 1500rpm fully warmed up. How it's at 850-900 rpm.

That's great but I noticed now when I drive the car and I push the clutch in. The rpm will drop so low that it kills the engine. I have to start the car back up and when I drive and let the clutch out it will drop again and sometimes it will go back up to 850-900 rpm but most the time it will stall and die.


I went ahead and disconnected the battery so and hopefully it's resets the ECU, that way the computer car re-learn with the vacuum leak fixed.

If that doesn't work, I'll have to raise the idle with the BISS screw.. What does everyone else think?


Update: I connected the battery and resetting the ECU didn't fix the problem. My idle is 1100, it doesn't die as much when pushing in the clutch but the rpms will drop to 100-200 and want to die before going back up to 1000 or so.

Not sure what the problem is. It's sounding like the IAC is dirty or something.

Can I use WD-40 to clean the IAC? Also do I have to separate the 2 halves to clean it or can I just clean the pintle?

Well I went ahead and bought a brand new IAC the new style, as mine was the old style(gold color). I'll see if it fixes the problem.

I checked the Dashpot and found the vacuum hose that should lead to the Dashpot check valve(black box) the little black box is missing on my car but I heard it isn't connected to any vacuum or pressure lines.

The Dashpot does seem a little weak as the rubber boot only depresses a little bit. I'm not sure if that is the problem.

I'm not sure if the Dashpot is the problem and I'm betting on the IAC being the culprit, as when I fixed that vacuum leak it was causing the idle problems.
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Last edited by ThatOneVr4; 11-18-2012 at 03:26 AM.
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Old 11-18-2012, 09:41 AM   #2 (permalink)
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Default Re: Found vacuum leak, now car dies

well I know the clutch is vacum assisted, maybe that might be the problem? IDk Just throwing things out there.
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Old 11-18-2012, 09:49 AM   #3 (permalink)
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Default Re: Found vacuum leak, now car dies

My car did the exact same thing I haven't fixed it yet cause I just spun a bearing. But I was told it could be two things the iac motor is weak. And are you running a open atmosphere bov try putting stock or a recirculating one in I will be doing this with y car once I get my new motor. I bought a brand new tb off of dbest well not brand new refurbished and I'm sticking a new iac in it so hopefully my car will run smooth and idle great again.
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Old 11-18-2012, 06:32 PM   #4 (permalink)
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Default Re: Found vacuum leak, now car dies

I'm running a open atmosphere bov. That could be the problem. I my 91 vr4 had the open bov and it ran just find but the IAC did go out on that car.

I'll slap the new IAC on when it gets here and see it that's the problem. If not I'll have to find the stock bov and see if that does the trick.

Edit: I might just try swapping the stock bov and seeing what happens. The more I read up about it, sounds like it could be from running a open atmosphere bov with the stock mas.

Since I had a vacuum leak it ran pretty good with the open atmosphere bov, not that it's fixed maybe it's stalling because of fixing the leak...

Last edited by ThatOneVr4; 11-18-2012 at 08:02 PM.
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Old 11-18-2012, 10:46 PM   #5 (permalink)
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Default Re: Found vacuum leak, now car dies

I just took off the ISC/IAC and it looks very very dirty. I don't have any electrical cleaner, so I used 91% rubbing alcohol.

I'm trying my best to wipe the dirt off but it's pretty caked on. It's still black in color.

Must be over 20 years of crud..I'll see how she runs after the cleaning but it might fix the problem when the new IAC gets here...
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Old 11-19-2012, 09:06 AM   #6 (permalink)
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Default Re: Found vacuum leak, now car dies

Let me know please
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Old 11-19-2012, 09:15 AM   #7 (permalink)
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Default Re: Found vacuum leak, now car dies

that Dashpot check valve(black box) i have one if ya need it shoot me a offer
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Old 11-19-2012, 10:00 AM   #8 (permalink)
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Default Re: Found vacuum leak, now car dies

did you put the check valve back in that hose?
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Old 11-19-2012, 10:44 AM   #9 (permalink)
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Default

Sounds like no check valve in the brake booster line...

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Old 11-19-2012, 02:07 PM   #10 (permalink)
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Default Re: Found vacuum leak, now car dies

Cleaning the IAC did the trick but had an electrical fire in my engine bay, so now I'm trying to excess what the damage is.
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