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  #1  
Old 03-24-2015, 08:46 AM
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E70 Hi RPM Engine Idle with A/C & BMWWHAT APP Code

I've been annoyed with the high rpm idle with the A/C engaged. The X5 feels jerky and changes the low speed dynamics.

In looking through the BMWAPP codes, I notice a CODE to change the high idle to normal with the A/C on. I've asked the dealer, but they said that's the way it was engineered, no idle speed adjustment. (they probably didn't know anyhow)

So - the question is: Why is the idle speed so high (900rpm) compared to NO A/C on (650rpm) and what was BMW trying to achieve? More A/C, emission issue?

If I change it back, can you think of any ill effects?

thanks,
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  #2  
Old 03-25-2015, 10:21 PM
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Most if not all cars increase the idle RPM when you turn on the A/C to keep the engine from stalling with the extra load from the A/C compressor.
Chuck
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  #3  
Old 03-26-2015, 02:57 AM
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Quote:
Originally Posted by PhastPhil View Post
The X5 feels jerky and changes the low speed dynamics.
,
Never a problem for me. Must not be driving at low speeds.

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  #4  
Old 03-27-2015, 09:25 AM
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Quote:
Originally Posted by ChuckG View Post
Most if not all cars increase the idle RPM when you turn on the A/C to keep the engine from stalling with the extra load from the A/C compressor.
Chuck
Hi Chuck,
Ever since fuel injection and ECU's, idle speed has been governed by a computer, therefore when an idle speed is set, say 650rpm, adding load: i.e.: drive or A/C, the ECU compensates and keeps the idle at the SET RPM - I'm all for that and it works very well. However, in the E70, when the A/C is on the idle is increased to 900+RPM from the 'normal' 650rpm.

My previous X5, E53, did not exhibit this issue OR our other BMW an E93 328I-C. With or without A/C the idle is steady at 650rpm. And as I noted there is a setting in the BMWAPP coding to reduce the idle speed with A/C on, to normal (650rpm).

When I refer to the low speed dynamics, I feel i'm 'fighting' the car as I slow down, like for a red traffic light or stop sign. The high idle wants the car to move faster than it feels when the A/C is off and the idle is 650rpm. I can modulate the brakes more effectively at the slower idle.

Soooo, the question was: Why did engineering at BMW increase the idle in the E70 to over 900rpm when other similar 6cyl BMW models with same engine, just use the normal idle of 650rpm with or without A/C engaged? My thought was either A/C efficiency or some emission issue.

And as a final note: thinking I was a bit too technical and critical, at a recent visit to the dealer on another issue, another E70 owner was complaining to my service writer about the same issue. It validated my concern.
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Phast Phil

328i Convert 2013 Ticket me RED. sometimes my wife lets me drive it LOL Tic'ed every option except Cold Weather PKG (we are in FL).
X5 2009 3.0 XDrive, Premium, Sat, ipod, Silver/Gray

Previous BMW's:
X5 2004 3.0
325e 1987 ("e" stood for exceptionally slow)
R1150 2001
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  #5  
Old 03-27-2015, 06:19 PM
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Just a data point, my '11 35d doesn't change idle speed with the A/C on, still 650ish...
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Old 03-27-2015, 06:49 PM
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Quote:
Originally Posted by PhastPhil View Post
Soooo, the question was: Why did engineering at BMW increase the idle in the E70 to over 900rpm when other similar 6cyl BMW models with same engine, just use the normal idle of 650rpm with or without A/C engaged? My thought was either A/C efficiency or some emission issue.
Idle speed is not a set value at all times - battery SOC, IHKA demands, gear engagement, electrical consumers, catalyst temps (based on models) are some factors which can influence the idle set point at any given time....but then again which engine do you have?
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Old 07-02-2022, 02:49 PM
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Sorry for resurrecting this but I have this exact problem with my newly acquired E70 3.0L. as far as I can tell this was a change up from BMW at the dealer level. I haven't been able to get my diagnostic connection working yet so I don't know if it's adjustable with INPA or DIS but I'm wondering what the reason was in the first place to bump up the idle with the A/C as much as they did? It's pretty annoying when driving in traffic and my vehicle sometimes spends a far bit of time idling with the A/C on which almost cancels out the gas mileage gain over the E53! ;( I know I'm really late to the party but anyone have any knowledge or experience with this ??
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Old 07-02-2022, 10:13 PM
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Quote:
Originally Posted by split71 View Post
Just a data point, my '11 35d doesn't change idle speed with the A/C on, still 650ish...
Jaja, sorry.I have no advice for you but I was.going to say the same thing. Get a diesel. Plenty of torque there. No idle change.
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Old 07-04-2022, 02:10 AM
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I use foxwell or bimmercode to adjust things. My rpm is definitely not 900 with AC but I usually bump it up at least 50 from factory I don't like being rocked like a baby at red lights. I have N55 wife has n63 motors i didn't catch yours
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Old 07-04-2022, 11:21 AM
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I have the 3.0l N52K. Are you saying you can adjust the idle speed to whatever you want ?(within a range I am assuming) At what speed does the car start rocking?
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