Intermittent Idle problem N51 128i

[rbtkoz]

My 128 started having an occassional intermittent bad idle. When at a light and engine warm it will jump 200 rpm and come back down, shaking the entire car a bit like a hiccup or maybe a misfire?!
This happens a few times a minute and gets worse the longer I idle. Less when engine is cold.
I just put in new plugs, properly gapped and torqued and new air filter and oil.
Car has 53k and is 2013 but did not have these symptoms prior.
No engine lights and no codes through carly. Checked the air box in case I had messed up the connection but everything is on tight. oil cap is on tight as well.
Planning on cleaning the MAF sensor next but does anyone have any idea what this could be?
Out of warranty but could I see if this could be part of sulev warranty?

[Dackelone]

Generally when the engine shakes at idle or at speed... it means your engine has a misfire. When it happens at speed it feels like you ran over something in the road. The car will really shake!

It could be a bad spark plug/coil pack or oil leaking onto the coil. Plugs on a 128i are supposedly good for a 100K miles. I would probably replace them sooner at 60K bc I plugs are cheap and easy to replace and I wouldn't want them to seize up in those holes.

First thing you need to do is read the car's fault memory with a bmw scan tool(not a generic scan tool).

[rbtkoz]

Thanks. Actually I did replace the plugs twice. First with Bosch then with NGK Laser. I didn't see any oil on the coils. Plugs were gapped and torqued correctly. I have this weird feeling that the issue happened after the sparkplugs change. The car was running great for 30 mins and then started to shake and feel like being kicked at idle. Really odd. Double checked coils and connections and everything is on tight. I guess I'll call the dealership and setup an appt to read the code and try to see if the sulev warranty approach will work.

[rbtkoz]

There were no codes car is clean. We did an update but this didn't fix the idle problem.
So intermittent idle from 700 to 600. Engine shakes, but has plenty of power. No problems otherwise and no engine faults stored.

It's not the sparkplugs since i've tried a few sets.
It's not the air filter since its upstream from Maf.
Could it be the oil change? The oil cap is on tight and level is a notch under max. Could the oil filter be causing a problem? Maybe I installed it incorrectly?
or could it be coils?

[crowtrobot]

Originally Posted by rbtkoz

There were no codes car is clean. We did an update but this didn't fix the idle problem.
So intermittent idle from 700 to 600. Engine shakes, but has plenty of power. No problems otherwise and no engine faults stored.

It's not the sparkplugs since i've tried a few sets.
It's not the air filter since its upstream from Maf.
Could it be the oil change? The oil cap is on tight and level is a notch under max. Could the oil filter be causing a problem? Maybe I installed it incorrectly?
or could it be coils?

I was getting some idle surging after I installed headers last week. Ran without codes for a while, then threw some misfire codes, which cleared and didn't return while the surging continued.

I disconnected the battery for a while to do some other work and when I drove it again after, the surging was gone. The DME must have lost the fuel management adaptations* and things smoothed out.

Might not help, but it's an easy test to try.

*Supposedly you can do this by turning the car ON (one button press, no engine), wait 15s, hold the throttle for 30s, then wait another 15s and turn it off, but I did not have luck doing this.

[rbtkoz]

Ok since the latest update of the BEM didn't solve my idle problem the assumption is the software side is not the issue.
Focusing on electric issues first from simple to complex.
Sparkplugs have been verified as not the issue by testing 2 different brands. The issue was replicated with both Bosch and NGK.
I Just purchased 6 new coils and will install with some dielectric grease to see if I can get the issue to replicate.
Still no stored faults and idle gets worse proportionally with time spent in idle.
Will update on success and failure in the next few days.

[rbtkoz]

Good news. Replaced the coils today and dabbed some dialectric grease on each. So far have not had the issue reappear after a few short drive. Will take a longer drive tomorrow to confirm.
Positive outcome is that the car starts much faster, it seems with less crank cycles.