No CEL, odd idle and hesitation/stuttering while driving.

[Bluey//M]

Hey all,

Been driving my E92 M3 which I bought used for about a month now and an issue has come up where the car has a violent shake at idle which feels like the car stops for a brief pause. You can hear the exhaust cut out as well, which to me seems like a misfire. It does this every 5 seconds, while driving between 1-3k rpm it pauses and hesitates and continues to do so after 3k but very sporadically.

I'm guessing coils/spark plugs may the culprit. The thing is if it were anything else, do you think a CEL would have already popped up?

Thanks

[opihi5]

Check codes, could be the idle-control valve.

My car threw an idle control valve error code after a rough idle 1-2.5k rpm. I immediately shut the car off and re powered and the code/problem has never came back.

[Bluey//M]

Originally Posted by opihi5

Check codes, could be the idle-control valve.

My car threw an idle control valve error code after a rough idle 1-2.5k rpm. I immediately shut the car off and re powered and the code/problem has never came back.

I'm getting P0308

Also I dont think idle control valve would cause an issue while driving, would it?

[monterey]

I had a honda civic that did that. It was a bad coil.

[BPMSport]

Replace coil and plug on cylinder 8.

[opihi5]

Originally Posted by Bluey//M

I'm getting P0308

Also I dont think idle control valve would cause an issue while driving, would it?

How many miles? Spark plugs sound like a good start.

[Bluey//M]

Originally Posted by opihi5

How many miles? Spark plugs sound like a good start.

82K

[Bluey//M]

Originally Posted by Mike Benvo

Replace coil and plug on cylinder 8.

Would that also explain when I floor it it sits flat on its face for a half second and then goes.

[BPMSport]

Originally Posted by Bluey//M

Would that also explain when I floor it it sits flat on its face for a half second and then goes.

Yes, a bad coil can cause that.

[Bluey//M]

Originally Posted by Mike Benvo

Yes, a bad coil can cause that.

Appreciate the help, I'll be grabbing your tune once she's good to go. Going to get all 8 plugs and coils replaced and then do a fuel injector cleaning (the professional way). New bearings in the summer!

[BPMSport]

Originally Posted by Bluey//M

Appreciate the help, I'll be grabbing your tune once she's good to go. Going to get all 8 plugs and coils replaced and then do a fuel injector cleaning (the professional way). New bearings in the summer!

Great idea. Because of the way misfire monitoring and knock detection is configured, you can have thousands of events in a particular cylinder without ever setting an engine light over a long period of time. It's a terrible design. In order to set a light, you have to have X amount of misfires per every 200 crank revolutions. So if you misfire every 201 revolutions it acts like everything is A-ok, when in actuality it's not.

Most of the time it won't set a light unless the coil is completely dead or harsher conditions like full throttle cause it to fall within that window.