[Itogliano]

Car has been lurching at low speed lately, mechanic reset the transmission shifting logic which seemed to help but reverted after a few days. Read that spark plug deterioration could be a cause so decided to change out plugs this past weekend. Also decided to put new coils in (they didn’t seem to be bad but with 110k miles I figured it wouldn’t hurt). Plugs have ~50k miles on them.

They look like they may have been running a little lean to me based on the white discolouration but curious to hear what people here with more experience/knowledge than me think.

I know this isn’t the proper cylinder numbering but for convience call them 1-6 (left to right, left is cylinder closest to front, right is rearmost). While changing them out, plugs 4 and 5 almost seemed seized in place, really had to wrench on them to get them to break free. The other came out no problem. I did the replacement back at 60k miles and torqued to spec so don’t know what caused that.

[Itogliano]

Forgot to mention, after changing plugs, car seems to be running smoother but I immediately had to take a different car for the week that's getting some work done so haven't really had a chance to evaluate if lurching issue is resolved yet

[RAK92]

I have yet to change the plugs on my BMW but the threads look awfully rusty. I know they don’t recommend to put anything on the threads, but the plugs I’ve removed in other cars didn’t have that much corrosion on the threads. Were your previous plugs like this as well?

[Itogliano]

Originally Posted by RAK92

I have yet to change the plugs on my BMW but the threads look awfully rusty. I know they don’t recommend to put anything on the threads, but the plugs I’ve removed in other cars didn’t have that much corrosion on the threads. Were your previous plugs like this as well?

It was long enough ago (and I don't have any pictures) that I don't really remember but I certainly don't think so... Don't put anything on the threads, per specs so I have no clue what could have caused it (don't know how moisture would have gotten in there, didn't leave the cylinders exposed for any prolonged amount of time).