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  #1  
Old 05-16-2011, 11:11 AM
rj7630 rj7630 is offline
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Stumble on cold start

When I start the car from cold, it starts immediately but then the idle drops and it stumbles around for a few seconds before finding a stable idle speed. After that it runs perfect and idles flawlessly.
I'm new to Subaru's and the SVX, not not sure what/how the cold idle is controlled and what might cause this.
It is a 94.
Thanks
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  #2  
Old 05-16-2011, 11:24 AM
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Nemesis Destiny Nemesis Destiny is offline
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Re: Stumble on cold start

I've been getting a stumble on cold starts lately too, except mine will quit if I give it any gas, and sometimes won't stay running. When warmed up, it's fine.

I suspect that it may be a fuel pressure issue, possibly fuel pump on its way out, because if I cycle the key on-off a couple times to prime the pump a few times, it doesn't do this.

Not sure if our two issues are related.
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1994 LSI The legendary "Shotgun Slade" 110k mi and still going strong!

2005 Outback XT Limited 5MT, Obsidian Black Pearl, 211k km, daily driver.
1999 Mazda MX5 base 5MT, Twilight Blue Metallic, 152k km. "Twilight Sparkle" Summer daily driver!
2007 Honda CR-V, some awful shade of light green *yawn*

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Old 05-16-2011, 11:28 AM
Cam Cam is offline
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Re: Stumble on cold start

Quote:
Originally Posted by Nemesis Destiny View Post
I've been getting a stumble on cold starts lately too, except mine will quit if I give it any gas, and sometimes won't stay running. When warmed up, it's fine.

I suspect that it may be a fuel pressure issue, possibly fuel pump on its way out, because if I cycle the key on-off a couple times to prime the pump a few times, it doesn't do this.

Not sure if our two issues are related.
You need to check yur coolant temp sensor with an ohm meter. I posted the factory specs here not long ago and if you go tbrough my posts you should find it rather quickly.

As for the OP, I would check vacuum at the manifold and fuel pressure between the filter and fuel line under the intake manifold. Make sure that the pressure stays up once he key is off, to eliminate the chance of a fuel leak.
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Old 05-16-2011, 11:33 AM
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Re: Stumble on cold start

That makes a lot of sense, since I've also been getting erratic rad fan behaviour to boot.

This is why I'm not a mechanic after having spent the better part of the last decade trying
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1992 LS-L Touring, Liquid Silver w/ Black, 110k mi. "Alice." Rebuilt title. Mods: WRX 6-CD changer, 17x8" Motegi LC-12 (16.5lbs), PWR rad, Perrin LCP, JDM v.8 6MT + R180, Koni + Ground Control (325f/280r), Earthworm Bushings. Awaiting resto.
1994 LSI The legendary "Shotgun Slade" 110k mi and still going strong!

2005 Outback XT Limited 5MT, Obsidian Black Pearl, 211k km, daily driver.
1999 Mazda MX5 base 5MT, Twilight Blue Metallic, 152k km. "Twilight Sparkle" Summer daily driver!
2007 Honda CR-V, some awful shade of light green *yawn*

1992 LS-L Touring, Ebony Mica, 176k kms. Parts car. SCRAPPED.
1992 LS-L, Dark Teal, 367k km. "Wintergreen" the winter beater.*SCRAPPED due to rust*
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Old 05-16-2011, 11:36 AM
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Chuckls Chuckls is offline
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Re: Stumble on cold start

Coolant temp sensor will fix it..the sender portion with the wires might be broke..That was the cause of mine.
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Old 05-16-2011, 03:27 PM
rj7630 rj7630 is offline
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Re: Stumble on cold start

thanks for the input. I'll check the temp sender. Actually I'll probably just replace it.
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Old 05-16-2011, 04:47 PM
Cam Cam is offline
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Re: Stumble on cold start

There is no need to just replace it. With an ohm-meter it is very easy to test. 2k to 3k ohms when cold (65 degrees) will tell you it functions properly when cold.
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'92 Ls-L Dark Teal
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Balanced & Blueprinted
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Old 05-16-2011, 05:23 PM
oab_au oab_au is offline
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Re: Stumble on cold start

Quote:
Originally Posted by rj7630 View Post
When I start the car from cold, it starts immediately but then the idle drops and it stumbles around for a few seconds before finding a stable idle speed. After that it runs perfect and idles flawlessly.
I'm new to Subaru's and the SVX, not not sure what/how the cold idle is controlled and what might cause this.
It is a 94.
Thanks
I was reading this post and my wife, looking over my shoulder, says that the choke is not working. Of course she is almost right.

If it starts immediately then the temp sensor is reading the temp and injecting the right amount of fuel. Maybe the Axillary Air Valve is not opening to give the fast idle that keeps it running for the 15 sec or so, till the Idle Air Valve takes over.

Harvey.
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  #9  
Old 05-16-2011, 07:49 PM
rj7630 rj7630 is offline
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Re: Stumble on cold start

On mine, it starts and revs up perfect for about a second. Then dies off and makes you think maybe it is going to quit, but catches it self and stumbles for maybe two seconds and then smooths out and runs perfect.
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