Fault codes 19 and 44
 

I've been getting 19 and 44 fault codes.

2003 E53 3.0L 6 cyl
88k miles

19 - #1 cyl misfire

44 - knock sensor cyl 5-6

Occasionally engine starts up rough and will smooth out again. Last time I changed all plugs and swapped the #1 coil with another to see if the problem moved throwing a different fault code. Also had an Oxygen sensor fault code so replaced both of the front O2 sensors with Bosch. All faults cleared. Rough start went away. I figured the knock sensor was a result of the rough idle and not the cause.

Life was good. No service light for months.

Then the service light came back a couple months ago and 19 and 44 show up again. Cleared the codes and they come back along with engine check light.

Rough start on Thanksgiving, but not as bad as before. Cleared codes... now back again.

Had time today to:
- Check plug #1 and compared to #2 and #3. No difference, tan color.
- Swapped #1 & #2 plugs and will see if code changes and follows plug.
- Swapped coil in #1 and #3 position to see if code changes and follows coil.

If the codes don't clear or change to follow the plug or coil, are there any suggestions for the next step besides take it in? Last time I had a rough start I took it to my service dude and he couldn't find anything wrong.

I'm running out of ideas and I have to pass smog. Thanks!

Have you replaced the knock sensors

The knock sensors are under the intake manifold, otherwise it would be the next step. I've got too many irons in the fire to not have the X running at the moment and would have to take it in to get those get replaced.

I'm hoping to find something I might have overlooked or not considered to get through a smog cert in the short term.

I replaced knock sensors on my daughters old Maxima this summer and it didn't resolve the fault codes or issues so I'm hesitant to jump to that as a fix here as well. She's now driving a slightly used Subaru :driver:

Reset the fault codes after the plug and coil rotation and the service light stayed out.

Drove around a few days after that and the X passed smog with no other changes made.

Life is good once more.