# RPM dropping at Idle



## VictoryRed08 (Feb 16, 2011)

I've noticed a couple of times now when I'm sitting with my foot on the brake while I'm idling a stoplight that the RPM will drop to about 500rpm (it normally sits around 1000rpm at idle) and the engine will "rattle" as if were going to stall.

Has anyone experienced this or know what it might be? The dealer basically said unless they can produce the issue, I'm SOL.

Thanks in advance.


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## montgom626 (Jan 16, 2011)

VictoryRed08 said:


> I've noticed a couple of times now when I'm sitting with my foot on the brake while I'm idling a stoplight that the RPM will drop to about 500rpm (it normally sits around 1000rpm at idle) and the engine will "rattle" as if were going to stall.


When warm, mine is 700 rpm "like a rock"

Maybe AC on and off?


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## 70AARCUDA (Nov 14, 2010)

...either A/C cycling on/off...or, might it possibly be the transmission prematurely shifting back into lock-up at the stop?


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## VictoryRed08 (Feb 16, 2011)

70AARCUDA said:


> ...either A/C cycling on/off...or, might it possibly be the transmission prematurely shifting back into lock-up at the stop?


No idea, I do notice that when I'm on a hill if I stop for an extended period of time I begin to roll backwards once I let off the brake, but that is the transmission shifting into neutral correct?


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## 70AARCUDA (Nov 14, 2010)

...yes. What they need is the old "hill-holder" that Studebakers had!


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## Serjuro (Mar 15, 2011)

*Mine*

Hello, mine is sitting at 850rpm, when engine is warm.
When starts on cold days, it idle between 1100 and 850rpm...........for few minutes............
The rpm also drops when the AC kicks in, but only for a moment......


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## Cruzemeister (Mar 22, 2011)

VictoryRed08 said:


> I've noticed a couple of times now when I'm sitting with my foot on the brake while I'm idling a stoplight that the RPM will drop to about 500rpm (it normally sits around 1000rpm at idle) and the engine will "rattle" as if were going to stall.
> 
> Has anyone experienced this or know what it might be? The dealer basically said unless they can produce the issue, I'm SOL.
> 
> Thanks in advance.


 I've noticed EXACTLY what you're describing. It dosen't do it "often", but it's exactly as you said. No, there is no A/c on. No, no and no to the other guesses. I noticed it usually after a good romp on a open highway, then coming to a stop at the exit ramp or stop light etc. You got your foot on the brake and it shivvers or shudders for about a second like it was gonna stall, but it catches itself and goes right back to normal idle. This is on an automatic LS. I haven't taken mine in for the 30 day free checkup yet, but I'm sure it will come under the "normal or can't duplicate it" list. 
My guess is it's just another weird quirk of the more complicated and busy 6 speed that gets a little freaked out under certain conditions. 
As I said in prior posts, it's a great car at a great value. But I do get goosebumps just thinking about what the future holds for cars like the Corvette for example if the engineers are going to continue to tinker with the laws of physics as they relate to internal combustion engines and the limitations of fuel conservation. 
As for tweeks and changes and TSB's, let me just say that there was a time in history when engineers lost their jobs if certain products didn't provide total customer satisfaction. If manufacturers allowed returns for product weirdness, I guarantee we wouldn't be having these conversations.


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## WHITECO (Mar 31, 2011)

From what I know about tuning...which isn't much 

I had a GMC Sonoma that I could tune with my laptop and as I modified it I found that I got that problem. What I learned is there is something called a Idle Air Control and what happens is the computer sets the RPM's at idle based on several factors. What most likely has happend is at a certain temperature/rpm there is a hole in the tune-up in the computer that GM put from the factory and at that temperature/rpm etc it get's confused and the idle drops.

I would only be worried if it stalled, it is perfectly fine for the idle to bounce around a bit, it isn't hurting anything.

Hope this helps?


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## 72buickgs (Mar 20, 2011)

a 1000 rpm at idel is to high. my '08 astra with 5spd shift, occasionally will drop below normal idle when i come to a red light or stop sign. the car never stalls. my understanding is that it is normal.


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## 72buickgs (Mar 20, 2011)

70AARCUDA said:


> ...yes. What they need is the old "hill-holder" that Studebakers had!


I remember that with the studebakers. that started around 1950. i just read an article in "old autos" newspaper, last night about a 1950 (?) studebaker pickup and that fact was noted.
subaru had something similar many years later.


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## WHITECO (Mar 31, 2011)

72buickgs said:


> I remember that with the studebakers. that started around 1950. i just read an article in "old autos" newspaper, last night about a 1950 (?) studebaker pickup and that fact was noted.
> subaru had something similar many years later.


My 1982 Subaru Wagon had the hill hold....that was a nice feature!!


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## Bossy70 (Feb 25, 2011)

VictoryRed08 said:


> I've noticed a couple of times now when I'm sitting with my foot on the brake while I'm idling a stoplight that the RPM will drop to about 500rpm (it normally sits around 1000rpm at idle) and the engine will "rattle" as if were going to stall.
> 
> Has anyone experienced this or know what it might be? The dealer basically said unless they can produce the issue, I'm SOL.
> 
> Thanks in advance.


I have gotten the same type of thing a few times (3,000 miles now). Don't know if its engine or transmission. It is not A/C. One of the times I had it off. And it didn't even happen right when I stopped, but maybe 5 seconds after... which it seems like the tranny should have been set in a gear at that point. I dunno... I thouht it was gonna shut off : )


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## eljackso (Apr 23, 2011)

My 6-speed manual ECO does this occasionally, too - so it isn't just the automatics. I believe it is the variable output fuel pump; the few times this happened, I had just gotten off the Interstate at around 70mph and it dropped to around 500-600 rpm when i stopped at the end of the ramp. So far it hasn't been an issue, but I am keeping an eye on it - it is a little worrisome when it first happens; feels like the engine is right on the edge of stalling.


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## Gritts (Jan 23, 2011)

Like Whiteco said, it's probably something to do with the IAC. I bet its a computer related issue involving data from the IAC. The answer would probably be a change in ecm programming. Of course we may eventually get recall notices on bad IAC sensors. :banghead:


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## gt_cristian (Apr 7, 2012)

I just experienced the same issue. While stopped at a light (A/C and fan OFF, only the radio was on) I felt as if the transmission was trying to got from neutral into 1st gear and back. I saw the RPM go from ~850 to ~550 and back up to ~850 rpm 4 times.
It scared the cruze out of me that it was going to stall.
I have always ran on 91 Shell or Esso since I bought it and I was at about half the tank when this happened
12000 miles
2011 Cruze LT (1.4T, A/T)
The only sign I had (related of not): while in traffic a few weeks ago, I kept it in manual mode and I saw it stayed in 2nd gear when stopped. Usually it should go into 1st gear. But that was the only time that happenned.


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## vigil14 (Feb 24, 2013)

I've had my car fixed for PCV problems twice. Maybe it could be your PCV.


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## 808CRUZEHI (Oct 29, 2018)

I have that same issue with my 2014 Cruze LS 1.8L. It started few months ago progressively gotten worse. First was a small idle drop (around 100 RPMs). Now it almost dies out and has a weird noise every time the idle drops. My car died at the stop light only once, but still does not show a check engine light. The longer I drive the worse the idle problem 
(idle drops down to 600 RPMs) almost dies. still trying to figure out the problem. If anyone has solved it please let me know.


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