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Discussion Starter #1
This just started two days ago. I start the engine and it has a very lumpy idle when cold. Ambient temp is not a contributing factor as it does it in the cool morning or hot afternoon. The car has 12k & no mods other than a crank pulley and pitch stop. After a couple of minutes when the engine is warm it idles fine. Noting one other thing it has always done that has been a concern is when coming to a stop and depressing the clutch pedal the RPM's drop almost to a stalling point then it recovers?

I will be taking it to the dealer for diagnosis and repair, just wondering if anyone else has experienced this issue and what might be the cause?
 

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Not sure about the lumpy Idle when cold, but I noticed RPM drop on my 2008 WRX and brought to a dealer and they said that it is normal and they all do this, however it isn't as noticable on my 2012 WRX.
 

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I would be willing to bet that the reduction in load from the lw crank pulley is causing both of your issues. Which one are you using?
 

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Discussion Starter #4
The Cobb pulley. It has been in place for about 7 months with no issues.
 

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Discussion Starter #6
It has been two weeks since installing the pitch stop.
 

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why was the pulley one of the first and only things you've done?

I've read where lightened pulleys can cause some roughness in idle.
 

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Discussion Starter #8
Main reason I did the pulley was due too the time it took the rpm's to drop between shifts.
 

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Interesting. Has it made a difference?
 

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My guess it the pulley, I have seen on other cars lightweight pulleys causing idle issues.
 

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Discussion Starter #11
I would guess pulley also. But it has not done it since yesterday with 4 cold starts since. I am going to look for a loose vacuum hose or something else loose. I am going to clean the MAF also. I would think if it were the pulley it would have manifested itself long before and be at every idle. Since it only happens when the engine has sat for at least 8 hours it may have something to do with cold engine emissions?
 

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I would guess you notice it now because of the pitch stop.
 

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Discussion Starter #14
The pitch stop is like night and day... That and the Cobb shifter bushing is money well spent!
 

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Discussion Starter #15
Started cold engine this morning and fine, nothing loose or leaking. Oh well then, if it does it again I will video it and take it to the dealership for them to figure out.
 

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Why did you put a Cobb crank pulley on the car? That's a really weird first mod (and they're pointless).
 
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