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      10-02-2019, 01:26 PM   #1
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lumpy idle - intermittent

From time to time I feel what appears to be lumpy idle, although on the digital tach the needle does appear to be fluctuating up/down too much, its usually in the 700rpm range. This caught my attention several times already as I'm sitting at a red light.

From what Ive noticed it mainly happens few minutes after the car had been started and had not been operated for several hours.

I mainly drive the car in M1 model, engine SS rest on comfort. When it happens, I feel the car rocking a bit side to side, like it has a cam lol, very faint of course, not like my Nissan motor with tomei 260 cams.

Has anyone experienced anything similar?
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      10-02-2019, 01:46 PM   #2
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Mine does this as well in the morning when I am leaving for work, but it stops after about a few hundred yards of driving. Like you, its only when the car has sat for a long period of time.
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      10-02-2019, 01:47 PM   #3
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Ive experienced this and thought it had to do with my catless pipes, both primary and secondary. Engine coughs a bit at idle. Only sporadically. Not the norm. Interesting. I always thought a tune would adjust the mixtures or the timing and solve it but i never did the tune.
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      10-02-2019, 01:48 PM   #4
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Ive experienced this and thought it had to do with my catless pipes, both primary and secondary. Engine coughs a bit at idle. Only sporadically. Not the norm. Interesting. I always thought a tune would adjust the mixtures or the timing and solve it but i never did the tune.
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      10-02-2019, 01:53 PM   #5
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Mine does this as well in the morning when I am leaving for work, but it stops after about a few hundred yards of driving. Like you, its only when the car has sat for a long period of time.
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      10-02-2019, 02:03 PM   #6
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Quote:
Originally Posted by hybrid_eg View Post
From time to time I feel what appears to be lumpy idle, although on the digital tach the needle does appear to be fluctuating up/down too much, its usually in the 700rpm range. This caught my attention several times already as I'm sitting at a red light.

From what Ive noticed it mainly happens few minutes after the car had been started and had not been operated for several hours.

I mainly drive the car in M1 model, engine SS rest on comfort. When it happens, I feel the car rocking a bit side to side, like it has a cam lol, very faint of course, not like my Nissan motor with tomei 260 cams.

Has anyone experienced anything similar?

Mine does this but its subtle. I think only my OCD ass would feel it. Mine is S+ across the board.
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      10-02-2019, 02:05 PM   #7
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Quote:
Originally Posted by hybrid_eg View Post
From time to time I feel what appears to be lumpy idle, although on the digital tach the needle does appear to be fluctuating up/down too much, its usually in the 700rpm range. This caught my attention several times already as I'm sitting at a red light.

From what Ive noticed it mainly happens few minutes after the car had been started and had not been operated for several hours.

I mainly drive the car in M1 model, engine SS rest on comfort. When it happens, I feel the car rocking a bit side to side, like it has a cam lol, very faint of course, not like my Nissan motor with tomei 260 cams.

Has anyone experienced anything similar?

Mine does this but its subtle. I think only my OCD ass would feel it. Mine is S+ across the board.
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      10-02-2019, 02:37 PM   #8
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Yes. Typical For V8s that makes as much power as some 12cyl engines (the rocking). I think the car is fuel sensitive. Once in a while I have a lumpy idle at cold start but I don’t drive it daily.
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      10-02-2019, 03:19 PM   #9
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i have noticed something exactly similar...im not sure what it is or could be...
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      10-02-2019, 03:55 PM   #10
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Thanks gents! Yes "rocking" best describes it.. feels like I'm sitting in a 60's V8 muscle car as long as I'm not the only one who felt it all good, doesn't seem to be affecting the car in a negative way besides that i noticed it like rest of you did.. and sure we all have some OCD ;-) btw, the only mod i have is Remus exhaust and i noticed this after exhaust.
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      10-02-2019, 08:09 PM   #11
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I feel more comfortable now, I'm not alone on this lol. Mine does it sometimes even when it was stock, I took it to dealer one time and they told me it's normal on this car.
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      10-02-2019, 09:52 PM   #12
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Could it be related to the Octane level of the gas being used?
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      10-02-2019, 10:39 PM   #13
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Same happens to my car and I actually thought it might be misfiring or something. Guess I’m not alone
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      10-03-2019, 06:55 AM   #14
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If the rough idle you're experiencing is prior to the engine having warmed up, then that is completely normal. On pg. 272 of the owners manual it states, "During engine warm-up phase, the V8 high-performance engine has a somewhat rougher running behavior because of the emission controls."

If the engine is fully warmed-up and running rough, that's not normal behavior.
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      10-03-2019, 01:11 PM   #15
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I'll watch for it next time and see if it does it when fully warmed up.. I've mainly noticed it a few minutes after start up.. doesn't matter if AC is on or off.. as i thought it might go away with AC having requiring higher amperage thus bumping idle a bit like it did on older cars.. i keep forgetting this is a 21st century vehicle ;-)
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      10-04-2019, 06:51 AM   #16
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Definitely notice this when the car has been sitting for a bit. Does not ever happen once warmed up.

Somewhat related. Just wondering if anyone else has noticed how loud the lifters are on this engine? I don't recall my previous M cars having that issue. I plan to ask the dealer at my next service.
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      10-04-2019, 08:53 AM   #17
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I have 3k miles on car and starting to notice it happening more. More ofter if i start the car with engine in S+.

Has anyone had failure of the engine start/stop not turning on when you release the brake? Car just dies and i have to hurry up put in neutral and manually start the car. I'm thinking it maybe the fuel pump.
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      10-04-2019, 12:00 PM   #18
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Quote:
Originally Posted by srttan View Post
I have 3k miles on car and starting to notice it happening more. More ofter if i start the car with engine in S+.

Has anyone had failure of the engine start/stop not turning on when you release the brake? Car just dies and i have to hurry up put in neutral and manually start the car. I'm thinking it maybe the fuel pump.
I have the auto start / stop disabled but I'm experiencing something similar and more than likely related to the fuel pump. If I drive for a bit, shut off the car and then attempt to restart while the car is still somewhat warm, I'll occasionally experience a shutoff. After this happens, it always starts up right away.

It happens here and there but I'm fairly certain your issue is probably related and more pronounced if you're utilizing auto start / stop.

I discussed briefly with SA and will address when the car's next in for service; he was in agreement that more than likely fuel pump related.
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      10-04-2019, 12:20 PM   #19
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Quote:
Originally Posted by ST3 View Post
Definitely notice this when the car has been sitting for a bit. Does not ever happen once warmed up.

Somewhat related. Just wondering if anyone else has noticed how loud the lifters are on this engine? I don't recall my previous M cars having that issue. I plan to ask the dealer at my next service.
I didn't notice the lifter noise on the F90.. on my F85 they are super loud on initial fire up after its been sitting overnight, then once the idle comes down and car warms up in couple minutes it goes away.
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      10-05-2019, 07:11 PM   #20
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what a relief that i am not the only one who has noticed this, first time i noticed this was shortly after i had installed the jb4, i guess being paranoid after instal made me more cautious and i noticed the slight rough idle at the first red light on the way to work in the morning. I thought it was a big dumb truck passing by or something until i realized its the car and since then almost every day i check to make sure i don't have codes lol...

it does go away after driving a little, strange that this happens, but glad I'm not misfiring lol
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      08-05-2020, 03:29 PM   #21
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So the swaying/ rocking during idle happened to me today. It has happened before but went away. Rpm fluctuates barely not all the time , feels like car is rocking side ways. I do have Remus catback and secondary delete and Eurocharged stage 1 with 5 gals e85 mix. Tune is not e30 flashed or anything. Check engine light for the first time came on, nothing in iDrive though. Connect OBD2 scanner and it said something to do with power train and emissions. Cleared the code n light went away. No codes for almost 50 miles but rocking is still there.

Any idea what it could be? I was suspecting lpfp as I do have rough start sometime and car shutting off but donno of it could be related on not. Also car drives fine no loss of power or anything.
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      08-06-2020, 12:48 AM   #22
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Yep I get this sometimes as well. Car feels rough and shakes slightly. I assume it's probably normal. Mine's stock.
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