bmw 128 coupe misfire??

[Bill128]

Hi all,

My 2013 128 has only 29K miles. In the last 1K miles it has started to do something at idle: Idling at a red light,it will make a "thunk...or...thunk-thunk.." at random intervals that you can feel but not necessarily hear. When it does this, the tach needle will drop a tiny bit with each thunk then bounce back up in between thunks. It is idling about 650 to 700 rpm. It is especially likely to do this with the AC on. revving the engine while sitting at the light to about 12-1500, engine is smooth with no thunks.

ALSO: If accelerating from a modest speed, with modest revs (like 1500) with very gradual throttle opening it's ok...but tip in the gas pedal maybe an inch more as though you want to accelerate more quickly, but not flat out, you will get a feeling like a misfire once or twice. If you mash the pedal to the floor, it's better; you might get one thunk then the car will accelerate smoothly.

If you use more revs in each gear...say 3500..you are much less likely to get a thunk.

From first or second gear mashing the pedal and running it to 6-7K is smooth as it should be.

I had the occasion to drive somewhere at 75-80 mph for an hour and it was better after that but it did not completely go away.

Now, I am tempted to blame my cheap self for driving too slowly (27 mpg) but I am still driving the same way and it didn't do it for the first 28K miles.

My previous cars would have flashed a CEL on dash for a mis fire but there is no light flashing or lit on my car.

So, has anyone experienced this and what was the problem???

TIA

PS: yes I tried top tier gas and two tanks with Techron in it

[mkeiser]

there might be a stored code that would clue you in

[Lester]

It could be s coil. Your symptoms are similar to my 135 when the coils were failing , but I got a yellow engine light.

[brake-fade]

I sent you a pm if you need to use a scan tool to check for codes. I'm in RI.

[jdt10768]

sounds like a coil going/gone bad, run codes

[nevetstoj]

Spark Plugs

[Bill128]

borrowed a tool to scan.
Got two codes.

2D15/not present. DME air mass sensor measurement range

and

A6CF/present. JBE: AUC sensor

First code went away when we cleared. I had cleaned the throttle body and air flow connection previously. So, this code is just stored, right?


Second code we cleared and it came right back. And I don't know what it is.

Any help here?

[Bill128]

Originally Posted by brake-fade

I sent you a pm if you need to use a scan tool to check for codes. I'm in RI.

I am not ignoring you. I can't find your message in my list of messages.

I did get a tool from some one and I posted the findings.

Can you shed any light on them?

[brake-fade]

If you disconnected the air mass sensor while ignition was off to access the throttle body, it should not cause an air mass sensor code. Air mass sensor issues will most definitely impact drivability. To be clear, was the stumble present before you cleaned the throttle body?The A6CF code should not impact drivability, as it relates to the climate control system recirculation, as I understand it.

[Bill128]

Originally Posted by brake-fade

If you disconnected the air mass sensor while ignition was off to access the throttle body, it should not cause an air mass sensor code. Air mass sensor issues will most definitely impact drivability. To be clear, was the stumble present before you cleaned the throttle body?The A6CF code should not impact drivability, as it relates to the climate control system recirculation, as I understand it.

I cleaned the throttle body and that sensor connection on the intake duct *because* I was having the thunk thunk at idle problem.

If you open the throttle a goodly amount in gears 3-6 at below 2000 rpm do you get that stuttering sensation....( I call it misfire but I dont know if that's what it actually is)

I am going out later today, I will get it full warm and let it idle a bit to see if it is still doing the thunk thunk. Thanks for you help. I am not much good on anything built after about 1977.

do you know how to get the throttle plate to fully open when the car is off so you can clean the body thoroughly? I had to have some one blip the throttle for me and I really can't see into it as it is placed low on the side

thanks for you help

[Bill128]

drove about 4-5 miles, stopped at a long light and watched closely. 650 RPM steady, then two thunks, dipping tach needle then back to steady. Only time it did it at idle on the trip of errands for 2 hours .

I did notice from about 2000 rpm in 4th or5th it did pull nicely when I opened the throttle a goodly amount.

If the weather improves I'll scan and see if the code is back because of the two thunks.

[Bill128]

OK,
Back here. Had Covid so, I was out of action.

Now, I cleaned the cabin open/closed filter and re ran the scan tool.

The only fault code I got this time was JBE2 Junction Box electronics.

The car is idling smoothly (5 min.) at 650 rpm without AC and 700 with AC.

This is a different code than before. I did a quick erase and it came back.

Any thoughts? TIA

[brake-fade]

Glad you're feeling better!
That code is pretty vague. So much information is being shared and read at that point that it really could be any number of things. It is also entirely possible that your issue has nothing to do with that code. I hate to say it, but you may just need to wait and see if it gets worse.

[Bill128]

Originally Posted by brake-fade

Glad you're feeling better!
That code is pretty vague. So much information is being shared and read at that point that it really could be any number of things. It is also entirely possible that your issue has nothing to do with that code. I hate to say it, but you may just need to wait and see if it gets worse.

Okay. It got worse. I pulled away from a stop sign flat out in 1st then second and it mis fired all the way...then it stayed on what felt like 5 cylinders with CEL flashing. I drove it another mile to the store. When I came out and restarted..it was fine then fine all the way home about 4 miles.

Now when I get the scan tool back, there should be a code stored in memory, correct? Feels like a bad coil pack?

[jdt10768]

See if you have an SULEV warranty on the car
If so, coil packs may be covered at dealership
If not, just replace them - sounds like you have at least 1 bad coil

[Bill128]

Originally Posted by jdt10768

See if you have an SULEV warranty on the car
If so, coil packs may be covered at dealership
If not, just replace them - sounds like you have at least 1 bad coil

car is 2013, would that be covered.

Also it is N52, which I think is not the extra low emissions engine. There were two engines available at the time.

I'll read the codes tonight. Hopefully it will tell me which cylinder is mis firing

[jdt10768]

Originally Posted by Bill128

car is 2013, would that be covered.

Also it is N52, which I think is not the extra low emissions engine. There were two engines available at the time.

I'll read the codes tonight. Hopefully it will tell me which cylinder is mis firing

It has to be labeled as SULEV under hood, and mine is an N51 (2013)
Also depends on what state you live in, so restrictions apply
There is a document detailing all the restrictions, but 15 yrs/150k miles is nice coverage

[Bill128]

Code: misfire cylinder # 5

So what? Replace that coil or all 6? Car is 2013 with only 30K miles.

[Bill128]

OK, so yesterday I replaced the #5 spark plug almost certainly unnecessarily (it looked perfect and was barely worn .002)

I also replaced all 6 coil packs.

Car is not misfiring in about 40 miles testing.

I cant re check the codes because my son has the reader. Maybe Monday

[Bill128]

So,
We cleared the codes. I had also replaced the AUC sensor.

They all went and did not return.

Last weekend drove 5 hours to Ticonderoga and 5 back and no misfires and no CEL. did not bother to re scan.

unfortunately, I knocked a jack point off the car so that's the next problem