# Fluctuating RPM At Idle



## Gus_Mahn (Aug 16, 2011)

It sounds like a vacuum leak. Most likely issues are a bad valve cover/PCV valve, or a valve cover leak, and it's getting pretty common on 1.4 turbo engines. My '12 Eco had this issue but with a CE light at roughly 75,000 miles. The valve cover was replaced under warranty for free.


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## trevor_geiger (Nov 29, 2012)

I've always wondered why it does that too.


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## Snappa (Mar 31, 2013)

Why does it go away once the engine drops rpm or go into closed loop?


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## Snappa (Mar 31, 2013)

Do you recall what code was put out for the CEL?


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## Gus_Mahn (Aug 16, 2011)

Snappa said:


> Do you recall what code was put out for the CEL?


 Mine had P0171 which is a lean code when my dealer replaced the valve cover. Some people get more than one code. 
It's possible that your car has a vacuum leak that's small enough that the car trims it up in closed loop, but it runs a bit off in open loop. Generally that sets a CE light.


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## Snappa (Mar 31, 2013)

Any way to convince the dealer to check it out and replace whatever part is leaking without getting hit with the "that's normal" or whatever because it's not throwing a code?


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## Robby (Mar 1, 2013)

It seems like the majority have noticed this condition, myself included.
I suspect the open loop programming is a bit flawed.....however, mine only does this three or four times at cold start then settles down.
Since mine is an auto, as soon as it's in gear and loaded the condition disappears.

I doubt, since it behaves normally once in closed loop, that there likely is no fix since in actuality, there is no problem with the car.
The condition seems to cause no harm.

Rob


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## obermd (Mar 3, 2012)

When I first start my ECO MT the idle will fluctuate. Once the car warms up it's fine. Now if you're fluctuating after warm up then you need to pay attention.


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## Merc6 (Jun 8, 2013)

obermd said:


> When I first start my ECO MT the idle will fluctuate. Once the car warms up it's fine. Now if you're fluctuating after warm up then you need to pay attention.


When you start, you let the clutch pedal go before or after the needles finish zero out sweep? If I hold it in after the needles sweep the the rpms jump. If I clutch in long enough to start and let go it stays normal.


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## obermd (Mar 3, 2012)

Merc6 said:


> When you start, you let the clutch pedal go before or after the needles finish zero out sweep? If I hold it in after the needles sweep the the rpms jump. If I clutch in long enough to start and let go it stays normal.


Depends on if I need to move immediately. If I've turned my engine off at a long red light and I start the engine when the other direction gets a yellow I frequently don't have time for the sweep to complete before I'm letting the clutch out. If I'm staring in the driveway I don't really pay attention to the engine speed until the car warms up. I have noticed that until the car goes into closed loop shifting can sometimes "race" the engine.


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