Uneven throttle during acceleration

Seagull · 04-18-2017, 06:37 PM

I'm experiencing a problem like the title says, and I'd like some opinions before I bring the car in.

The car is a 2012 e84 28i xdrive, 8AT, with close to 100,000km on it. I am the second owner.

Symptoms:

The car's acceleration feels "rough" from time to time. About 50% of the time
During coasting or cruising the car feels smooth.
The roughness does not feel like loss of power. It's more like little tugs on the curve when applying power. I.e. there is no dip or drop in the power curve. It's kind of like the feeling there is something tugging on the end of a line when you are fishing. Subtle but noticeable if you are the one fishing.
The symptom is a bit subtle in that most passengers would only notice if I told them. In addition if I were accelerating over a slightly bumpy road you wouldn't feel it.
If the road is new and smooth passengers might notice or would thinking that there was something wrong with my foot!
It usually occurs at certain rpm ranges. For example 2100-2500rpm and 3500-3800rpm.
It occurs in both D and DS modes. When I switch modes, it seems to move around in terms of which rpm
Sometimes, when coming to a stop and the car changes gears to neutral, there is a slight roughness. This could be unrelated to the above, but normally if the above occurs, this occurs as well.

Currently I have only done the MAF cleaning which was pretty easy.

What are your thoughts on what it might be? Since it's only 50% reproducible, I'm not sure I want to bring it in to a mechanic just yet. But if it's serious...

I'm not super mechanically experienced but what are the possibilities...
Timing chain?
Some sensors?
Valve Cleaning required?
Wiring harness, coils?

Gamb1t · 04-18-2017, 07:51 PM

Of the top of my head....

Bad gas
Fuel filter might need to be replaced
Take your air intake apart and look around for possible clog.
Oil on throttle body or intake manifold.... Hence some owners install oil catch can.
Could also be the turbo tract...Uppipe and down pipe.
See if you can check for any hidden codes.

kiloTHREE · 04-18-2017, 08:47 PM

I also get this around 3500-3800rpm under 1/2 to 3/4 throttle but only 1 out of 10 times.
Can get it to do it only when I actively try for a while.
I'd say it's more transmission coding related, it's almost as if it sees the normal shift point, says naaaaa maybeee wtf ok lets go to 4k then shift.

Seagull · 04-19-2017, 04:44 PM

Thanks for the suggestions. It doesn't sound too scary. I'll probably get it looked at next week and let people know.

Seagull · 04-30-2017, 08:56 AM

So here's an update.

I brought the car in for my rear brakes and asked for the uneven throttle to be investigated.

After keeping it for a day and driving it and checking codes and inspecting the car... they found nothing out of the ordinary and said 'it's normal for that engine '

At that point, I wasn't sure that they could reproduce it. Anyway I took the car back and.... can no longer reproduce it. It's gone and previously I could have easily reproduced it by now. Did it just go away right then or was something cleaned in the inspection process I don't know. But it's definitely gone.

I know. Sorry this doesn't help anyone with similar problems.

IslandTimes · 05-01-2017, 08:16 AM

Three ideas:

My wife's old car was a Nissan that experienced very similar issues. Turns out it was a faulty brake sensor. Maybe when they did your rear brakes that fixed the issue?

My X1 had a rough idle until I changed out the spark plugs. It's much smoother now.

I remember reading a while ago about inadequate grounding in our cars causing less smooth engine and transmission operation. The solution was to install a large diameter grounding cable at certain points on the car. I don't remember seeing anyone else besides the poster trying it, so they may have just been trying to sell something unneeded.

Seagull · 05-02-2017, 11:28 PM

Quote:

Originally Posted by IslandTimes

Three ideas:

My wife's old car was a Nissan that experienced very similar issues. Turns out it was a faulty brake sensor. Maybe when they did your rear brakes that fixed the issue?

Maybe. I'll have to drive it some more to see if it is gone...

04-18-2017, 06:37 PM	#1
Seagull Major 288 Rep 1,075 Posts Drives: F87 M2, E84 X1 Join Date: Jan 2006 Location: Toronto iTrader: (0)	Uneven throttle during acceleration I'm experiencing a problem like the title says, and I'd like some opinions before I bring the car in. The car is a 2012 e84 28i xdrive, 8AT, with close to 100,000km on it. I am the second owner. Symptoms: The car's acceleration feels "rough" from time to time. About 50% of the time During coasting or cruising the car feels smooth. The roughness does not feel like loss of power. It's more like little tugs on the curve when applying power. I.e. there is no dip or drop in the power curve. It's kind of like the feeling there is something tugging on the end of a line when you are fishing. Subtle but noticeable if you are the one fishing. The symptom is a bit subtle in that most passengers would only notice if I told them. In addition if I were accelerating over a slightly bumpy road you wouldn't feel it. If the road is new and smooth passengers might notice or would thinking that there was something wrong with my foot! It usually occurs at certain rpm ranges. For example 2100-2500rpm and 3500-3800rpm. It occurs in both D and DS modes. When I switch modes, it seems to move around in terms of which rpm Sometimes, when coming to a stop and the car changes gears to neutral, there is a slight roughness. This could be unrelated to the above, but normally if the above occurs, this occurs as well. Currently I have only done the MAF cleaning which was pretty easy. What are your thoughts on what it might be? Since it's only 50% reproducible, I'm not sure I want to bring it in to a mechanic just yet. But if it's serious... I'm not super mechanically experienced but what are the possibilities... Timing chain? Some sensors? Valve Cleaning required? Wiring harness, coils? __________________ Current: F87 M2 MT MPE, E84 PP SP LP Previous: F30 - 335i AT, E90 - 335xi MT, E90 - 330i MT, E46 - 330i MT
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04-18-2017, 07:51 PM	#2
Gamb1t Major 598 Rep 1,343 Posts Drives: 330i,X1,Z4,Solstice GXP, RX-8 Join Date: Aug 2015 Location: Canukistan iTrader: (0)	Of the top of my head.... Bad gas Fuel filter might need to be replaced Take your air intake apart and look around for possible clog. Oil on throttle body or intake manifold.... Hence some owners install oil catch can. Could also be the turbo tract...Uppipe and down pipe. See if you can check for any hidden codes.
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04-18-2017, 08:47 PM	#3
kiloTHREE Lieutenant 76 Rep 435 Posts Drives: '13 xDrive28i Join Date: Jun 2016 Location: MN iTrader: (0)	I also get this around 3500-3800rpm under 1/2 to 3/4 throttle but only 1 out of 10 times. Can get it to do it only when I actively try for a while. I'd say it's more transmission coding related, it's almost as if it sees the normal shift point, says naaaaa maybeee wtf ok lets go to 4k then shift.
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04-19-2017, 04:44 PM	#4
Seagull Major 288 Rep 1,075 Posts Drives: F87 M2, E84 X1 Join Date: Jan 2006 Location: Toronto iTrader: (0)	Thanks for the suggestions. It doesn't sound too scary. I'll probably get it looked at next week and let people know. __________________ Current: F87 M2 MT MPE, E84 PP SP LP Previous: F30 - 335i AT, E90 - 335xi MT, E90 - 330i MT, E46 - 330i MT
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04-30-2017, 08:56 AM	#5
Seagull Major 288 Rep 1,075 Posts Drives: F87 M2, E84 X1 Join Date: Jan 2006 Location: Toronto iTrader: (0)	Mysteriously fixes....? So here's an update. I brought the car in for my rear brakes and asked for the uneven throttle to be investigated. After keeping it for a day and driving it and checking codes and inspecting the car... they found nothing out of the ordinary and said 'it's normal for that engine ' At that point, I wasn't sure that they could reproduce it. Anyway I took the car back and.... can no longer reproduce it. It's gone and previously I could have easily reproduced it by now. Did it just go away right then or was something cleaned in the inspection process I don't know. But it's definitely gone. I know. Sorry this doesn't help anyone with similar problems. __________________ Current: F87 M2 MT MPE, E84 PP SP LP Previous: F30 - 335i AT, E90 - 335xi MT, E90 - 330i MT, E46 - 330i MT
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05-01-2017, 08:16 AM	#6
IslandTimes Enlisted Member 7 Rep 44 Posts Drives: 2013 X1 sDrive28i Join Date: Dec 2014 Location: Florida iTrader: (0)	Three ideas: My wife's old car was a Nissan that experienced very similar issues. Turns out it was a faulty brake sensor. Maybe when they did your rear brakes that fixed the issue? My X1 had a rough idle until I changed out the spark plugs. It's much smoother now. I remember reading a while ago about inadequate grounding in our cars causing less smooth engine and transmission operation. The solution was to install a large diameter grounding cable at certain points on the car. I don't remember seeing anyone else besides the poster trying it, so they may have just been trying to sell something unneeded.
	Appreciate 1 Seagull287.50 Quote