Hunting idle / hesitation...help?

jimbojsb · 01-19-2011, 10:45 PM

Over the past few days I've been having some engine trouble with my Z4MR. I have a service appointment next week but I wondered if anyone might have any thoughts as to the cause. Basically, it won't maintain a steady RPM at any point in the power band, but it's most pronounced when idling. It seems to dip around 200RPM and then the computer picks it up, and this will continue on indefinitely. I've tried running it under hard acceleration and you can definitely feel it hesitating with the same "pulse" that it has at idle. My thought is that this is a MAF or other sensor issue, but there is no check engine light on. If it only did this on a cold start or something, I wouldn't be worried, but it persists even after 10+ minutes of running and the oil temp is up.

The car has about 35k miles on it and had Inspection II done at around 28000

I took some video of it:

Any thoughts would be appreciated.

santov · 01-19-2011, 11:26 PM

I don't have an M, but when my N52 is cold it will hunt a little, maybe +/-300 RPM, but nothing like your video.

Once it's warm it doesn't hunt at ALL.

pokeybritches · 01-20-2011, 03:25 AM

Have you tried resetting the throttle adaptations or ECU? I know it's a long shot, but it's worth a try. Computers can do funny things and need to be reset every once in a while.

Do you hear any high pitched whistle/whine at partial throttle? A vacuum leak can cause rough idle.

onebluemcm · 01-20-2011, 07:54 AM

That is curious, subtle. I was expecting a greater fluctuation, vids good idea. I don't know if it will help, but I'll try to remember to check the TIS when I get home, see if there are any good tips in there - not holding my breath though....

jimbojsb · 01-20-2011, 08:16 AM

Sometimes it is more pronounced than others. At idle i've seen it dip by at most 300RPM. I tried it again this morning and really stood on it in 2nd and it was quite jerky all the way to 8000rpm. Going to spend the day today fiddling and see if anything makes a difference.

jimbojsb · 01-20-2011, 01:44 PM

Pulled the MAF sensor off the car and ran it for a few minutes without it. It made no difference at all, and also showed no check engine light, which is surprising. Thoughts?

01-19-2011, 10:45 PM	#1
jimbojsb Mthusiast 98 Rep 123 Posts Drives: Too Many Join Date: Jul 2009 Location: Austin, TX iTrader: (1) Garage List 2006 X5 4.8is [0.00] 2020 M4 Competition [0.00] 2001 740i [0.00] 2006 M Roadster [0.00]	Hunting idle / hesitation...help? Over the past few days I've been having some engine trouble with my Z4MR. I have a service appointment next week but I wondered if anyone might have any thoughts as to the cause. Basically, it won't maintain a steady RPM at any point in the power band, but it's most pronounced when idling. It seems to dip around 200RPM and then the computer picks it up, and this will continue on indefinitely. I've tried running it under hard acceleration and you can definitely feel it hesitating with the same "pulse" that it has at idle. My thought is that this is a MAF or other sensor issue, but there is no check engine light on. If it only did this on a cold start or something, I wouldn't be worried, but it persists even after 10+ minutes of running and the oil temp is up. The car has about 35k miles on it and had Inspection II done at around 28000 I took some video of it: Any thoughts would be appreciated.
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01-19-2011, 11:26 PM	#2
santov Lieutenant 64 Rep 483 Posts Drives: 2007 Z4 3.0si White over Beige Join Date: Dec 2010 Location: Bay Area, Calif iTrader: (8)	I don't have an M, but when my N52 is cold it will hunt a little, maybe +/-300 RPM, but nothing like your video. Once it's warm it doesn't hunt at ALL.
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01-20-2011, 03:25 AM	#3
pokeybritches Colonel 479 Rep 2,782 Posts Drives: ESS/G-Power Z4M, VF Z4, 996tt Join Date: Sep 2009 Location: Los Angeles iTrader: (12) Garage List 2006 BMW Z4M [10.00] 2006 BMW Z4M [8.50] 2003 BMW Z4 3.0i [9.00]	Have you tried resetting the throttle adaptations or ECU? I know it's a long shot, but it's worth a try. Computers can do funny things and need to be reset every once in a while. Do you hear any high pitched whistle/whine at partial throttle? A vacuum leak can cause rough idle.
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01-20-2011, 07:54 AM	#4
onebluemcm Captain 42 Rep 632 Posts Drives: '07 Z4MC Join Date: Apr 2010 Location: Richmond, VA iTrader: (0)	That is curious, subtle. I was expecting a greater fluctuation, vids good idea. I don't know if it will help, but I'll try to remember to check the TIS when I get home, see if there are any good tips in there - not holding my breath though.... __________________ \|=.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-.=\| Silbergrau A08 / Sepang Brown LSD6 / Carbon Leather 4MY (1 of 3, this combo) RAC RG63 \| Conti EC-DW \| GC/Koni-Dinan \| Rogue RSM \| Arqray \| Autosolutions \| BMW brace \| Pinnacle tint
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01-20-2011, 08:16 AM	#5
jimbojsb Mthusiast 98 Rep 123 Posts Drives: Too Many Join Date: Jul 2009 Location: Austin, TX iTrader: (1) Garage List 2006 X5 4.8is [0.00] 2020 M4 Competition [0.00] 2001 740i [0.00] 2006 M Roadster [0.00]	Sometimes it is more pronounced than others. At idle i've seen it dip by at most 300RPM. I tried it again this morning and really stood on it in 2nd and it was quite jerky all the way to 8000rpm. Going to spend the day today fiddling and see if anything makes a difference.
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01-20-2011, 01:44 PM	#6
jimbojsb Mthusiast 98 Rep 123 Posts Drives: Too Many Join Date: Jul 2009 Location: Austin, TX iTrader: (1) Garage List 2006 X5 4.8is [0.00] 2020 M4 Competition [0.00] 2001 740i [0.00] 2006 M Roadster [0.00]	Pulled the MAF sensor off the car and ran it for a few minutes without it. It made no difference at all, and also showed no check engine light, which is surprising. Thoughts?
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