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Engine races

From new, the engine in my 2005 2.5 liter Impreza occasionally races on start up. It has a 5 speed standard trans. The racing usually (not always) happens when I back out of my garage when the engine is cold. When the engine is warmed up and re-started, it idles normally.

I’ve had it to the dealer several times and they can not find the problem. They even checked download software patches to correct the problem – none exist. I’ve even contacted Subaru of America and obtained no results.

Any thought what the problem might be?


When cold, the engine is supposed to idle higher than normal. How much on the tachometer is the engine ‘racing’? And, how long does it do this before you shut it off? If it is 2,000 to 2,500 RPM, this may be considered normal. Higher than that may be a cause for concern.

Yes I’m aware that cold engines have a faster idle speed. The speed I’m see is about 2500 rpm. This is too fast and is not normal. This is my eight Subaru, and none of them ever had this problem. The Subaru dealer also agrees this speed is too fast.

If the dealer has ruled out any vacuum leaks or a bad IAC, maybe re-flashing the original programming to the ECM will fix it. Since there are no software patches available.

They re-programmed it several times – to no avail.
One thing I failed to mention in the original was if I started the (cold) engine and drifted backwards downhill, it is sometimes REALLY bad.

It’s probably a bad IAC. I can’t think of anything else if there are no vacuum leaks.