Odd idle at start up after work

The Bavarian · 08-10-2015, 07:38 PM

I've noticed a trend over the past month or so.
When I start the car at the end of the day ~5pm, it starts up quickly, but the idle hunts up and down for about 10 seconds.

Its always seemed a little odd. After about 5-8 increases to about 1,200 rpm and back down to about 700, it settles out and runs just fine.

Interestingly enough the sound doesn't correspond to the tach. When the tach is reading 1,200 the engine sounds like its at 700 and when the tach drops down the engine sounds like its spinning up.

When I start it up in the morning (cold) it doesn't do this at all.
Only after the long day out in the parking lot. It occurred today and I even drove it at lunch (and it didn't happen then)

Any ideas what I should be checking or doing to diagnose this issue?

bavaddict · 08-10-2015, 10:15 PM

Based on my personal experience, I would suggest the following:

1) Get the car scanned via INPA or any other BMW scanner. that may point you to underlying issue.

2) Check for leaky injectors and fouled spark plugs.

3) Carbon build up in intake could be an issue as well. Depending on mileage you may be due for one.

Hope this helps

08-10-2015, 07:38 PM	#1
The Bavarian Private 5 Rep 67 Posts Drives: 2011 335i e90 M-Sport, AT, PPK Join Date: May 2015 Location: Denver, CO iTrader: (0)	Odd idle at start up after work I've noticed a trend over the past month or so. When I start the car at the end of the day ~5pm, it starts up quickly, but the idle hunts up and down for about 10 seconds. Its always seemed a little odd. After about 5-8 increases to about 1,200 rpm and back down to about 700, it settles out and runs just fine. Interestingly enough the sound doesn't correspond to the tach. When the tach is reading 1,200 the engine sounds like its at 700 and when the tach drops down the engine sounds like its spinning up. When I start it up in the morning (cold) it doesn't do this at all. Only after the long day out in the parking lot. It occurred today and I even drove it at lunch (and it didn't happen then) Any ideas what I should be checking or doing to diagnose this issue?
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08-10-2015, 10:15 PM	#2
bavaddict Lieutenant 51 Rep 443 Posts Drives: F32 435i MPerf Edit Join Date: May 2010 Location: East Coast iTrader: (0)	Based on my personal experience, I would suggest the following: 1) Get the car scanned via INPA or any other BMW scanner. that may point you to underlying issue. 2) Check for leaky injectors and fouled spark plugs. 3) Carbon build up in intake could be an issue as well. Depending on mileage you may be due for one. Hope this helps
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