Still can’t figure it out - stumble/irratic idle

[turbosl2]

I have owned my 128 since 2010, has 62000 miles. I replaced the plugs at 40k. I have never had an engine light.

Issue/symptoms:
After a few minutes of driving SOMETIMES when I am stopped with car in gear and foot on the brake the tach drops a tad and it feels like the engine is stumbling. It always clears up after about 2-5 secs or I start to accelerate. Other times it will skip or stumble when coming off idle and LIGHT throttle. Just a miss or 2.

Engine light never comes on. I checked the INPA software and everything is normal.

I checked the cam sensor and no oil in the connector.

It’s hard to diagnose when it’s so quick and never throws an engine light or pending code.

Car always starts 100% fine and idles fine until you drive for a few minutes.

Ideas? I been trying to figure this out for years and waiting for something to fail so I can replace it. Still waiting!

[Dackelone]

My first thought was a bad coil pack. Until you mentioned that sometimes it happens when your foot is on the brake pedal. To me I am thinking your vacuum check valve for the brake booster might not be working properly.

On the 128i they have a mechanically driven vacuum pump. But there should be a check valve somewhere in the piping. Maybe hose #8 ? I really can't tell in the ETK.

http://www.realoem.com/bmw/enUS/show...diagId=34_1556

You might also have your dealer run your VIN... I know these vacuum pumps do go bad and have had some recalls on them. Its worth checking for any open recalls.


IF you have access to a code reader... I would also look at long term fuel trims to see IF you have a vacuum leak. A bad brake booster vacuum valve could cause that.

Also... when you replaced the spark plugs... did you use BMW dealer bought plugs? Some people have had issues like a weird idle or misfires with aftermarket plugs. IF your car has more than 80K miles... you should consider replacing all six coil packs too.

Dackel

[turbosl2]

I did use NGK plugs that seem to be to OEM equivalents. I can check INPA to see what the fuel trims are. I don’t believe this is the problem only because it’s so intermittent, some days all is fine. I was hoping coils but no silver bullet. I don’t want to just throw 6 coils at it and have no change. I would figure coils or plugs would throw a CEL

[twinboost_MD]

Do you have an auto or manual?

[mackeroni]

I have had similar symptoms from bad gasoline. Do you use top tier fuels?

[turbosl2]

I have an AUTO

[turbosl2]

Originally Posted by mackeroni

I have had similar symptoms from bad gasoline. Do you use top tier fuels?

Yes car ha only had 91 or higher

[Gangplank]

Originally Posted by turbosl2

Yes car ha only had 91 or higher

91 from Shell/Chevron

OR

91 from 7-11 or Stop-N-Go?

[turbosl2]

neither.
Sunoco or sspeedway(hess)

[chris_flies]

Try putting a bottle of Techron injector cleaner into a quarter tank of gas before refilling. It seems to be the cure-all for rough idles or "stumbles."

Costco's gas supplier is Top Tier. I go there as much as possible, it's about $.40 less expensive (I'm tuned, I have to run 93) than everything else, and better than a good portion of all else...

[turbosl2]

Unfortunately I have tried many injector cleaners and nothing helped

[jaye944]

sorry to come late to the party, did you use OEM plugs, apparently non-oen's have problems, also OEM's are pre-gapped

[jaye944]

from what I've heard additives don't do a lot, cleaners such as techron, that's not fixing the problem, weird no codes in INPA

that points away from a bad coil.

I still think plugs

[jaye944]

yeah exactly what dack is saying on the plugs, but' you'd throw codes for a bad coil pack

Originally Posted by Dackelone

Also... when you replaced the spark plugs... did you use BMW dealer bought plugs? Some people have had issues like a weird idle or misfires with aftermarket plugs. IF your car has more than 80K miles... you should consider replacing all six coil packs too.
Dackel

[turbosl2]

I did use the oem NGks. I just ordered another set , it’s been 20k miles. I am also replacing all the coils. Figure I give it a try for $170. Maybe one is acting up, idk but it’s gett more often but can’t wait any longer for a code in INPA

[turbosl2]

I just pulled the plugs and all looks well to me. Stuck my Wi-Fi iPhone boroscope in the cylinders and a small amount of carbon but all looks normal

[MightyMouseTech]

Originally Posted by turbosl2

I did use the oem NGks. I just ordered another set , it’s been 20k miles. I am also replacing all the coils. Figure I give it a try for $170. Maybe one is acting up, idk but it’s gett more often but can’t wait any longer for a code in INPA

I thought all the OE plugs were Bosch?

When I accidentally installed the N54 plugs in my N55, I was getting terrible misfires. Never showed any codes.

Edit:

Originally Posted by turbosl2

I did use NGK plugs that seem to be to OEM equivalents.

The ONLY place you can get OE plugs is at the dealer.

[turbosl2]

Originally Posted by MightyMouseTech

I thought all the OE plugs were Bosch?

When I accidentally installed the N54 plugs in my N55, I was getting terrible misfires. Never showed any codes.

Only on the turbo cars they are Bosch

[Dackelone]

Originally Posted by MightyMouseTech

I

The ONLY place you can get OE plugs is at the dealer.

^^Yep. But most people don't learn their lesson chasing after a erratic misfire on these cars. Their IS a difference between OE and OEM. But most don't know the difference like we do.

OP - go buy some plugs from any BMW dealer. Make sure they say "BMW Bosch" on them. There is a design difference(in the ceramic insulator) on the OEM aftermarket plugs(vs the BMW(OE) ones.

Dackel

[Dackelone]

Originally Posted by turbosl2

Only on the turbo cars they are Bosch

Nope. Well... kind of. BMW used NGK's and BOSCH plugs. But I bet the plugs bought from a BMW dealer are different to the aftermarket(OEM) versions.


http://www.realoem.com/bmw/enUS/show...diagId=12_1417


03 Spark plug, High Power NGK PLZFR6A11S 6 08/2009 12120035915 $21.32 ENDED

03 Spark plug, High Power 6 12/2009 12122158253
03 Spark plug, High Power BOSCH FR7NPP332 6
08/2009 12120032138 $21.32 ENDED
03 Spark plug, High Power 6 12/2009 12122158253

[turbosl2]

My car came with NGK plugs. The BMW plugs ARE exactly the same, same part number from NGK. The plugs being incorrect are not the problem. They were fine for many years. Maybe one is going bad or a coil is acting up but I won’t know until I swap everything to new the end of the week. I suspect there is something else going on and I can’t solve it because nothing in the computer shows an issue

[kb2wji]

My '11 128 is doing the same thing. It's very subtle (nobody notices but me) and it's only once in a while. If i'm at a stop light it might very subtly "hiccup" really quick. I did change my plugs with BMW OEM's about 6 months ago. I also changed the coil packs with the "high performance" red ones from BavAuto (apparently "high performance" is BavAuto speak for "chinese made crap"....I digress...) I'm going to try the fuel additive and see if that helps, but i'll be following this thread nontheless