[ezadel]

Ok So I was driving my E91 2008 328xi this morning and after about 10 minutes of driving I get check engine soon. With the code 0029 CF misfire in cylinder 3 and engine misfire hesitation. Now here is the deal. I changed coils and spark plugs not too long ago.
Also if I clear the code turn off the car and turn it on again it comes back right away

But if I clear the code turn off the car and let it cool down for 30 mins or so the the code ( and the misfire hesitation) is gone until I drive the car for about 15 minutes then it comes back with the hesitation.

Always cylinder 3 and only cylinder 3

Any suggestions for more tests. I have carly and can take live data if needed.
I am thinking leaky iniector and it takes 15 minutes for leak to become significant?

[dmatre]

Swap coils 3 & 1, then see if the code stays at #3, or if it moves with the coil.

[e91Owner]

Originally Posted by dmatre

Swap coils 3 & 1, then see if the code stays at #3, or if it moves with the coil.

This^^.
You didn’t say what coils you used on the replacement, but the older Bosch ones were particularly sensitive to temperature. May just have a bad coil.

[ezadel]

Originally Posted by e91Owner

This^^.
You didn’t say what coils you used on the replacement, but the older Bosch ones were particularly sensitive to temperature. May just have a bad coil.

This is super helpful. I had used the Bosch ones from FCP euro. It was a kit with spark plugs but now I remember one of the 6 was bad out of the box. I changed the coils from cylinder 3 to 2 and the error is gone I am waiting for it to reappear. I think it may have been a flimsy coil?

[dmatre]

It could also have been a loose connector. Swapping the coils may have fixed the problem.

When I replace my coils, all was good for a couple of days, then another misfire. When checking the offending cylinder, I found that I hadn’t fully secured the connector to the top of the coil.

Properly locking the connector resolved the problem.