2012 Acura MDX 3.7L V6
MIL on with misfire complaint.
This one is fixed, but I don't fully understand why it was broken, maybe someone will have a better idea.
This Acura would start and run well, for all of ten seconds. Then it would begin to misfire, bad, like you flipped a switch. Shut down and restart, exact same scenario.
Code scan revealed:
P0355-Crank sensor signal intermittent
P0302/4/6- misfire cylinder 2/4/6
P0300-random misfire
P0430-cat efficiency B2
I verified that those 3 cylinders were indeed a dead miss, all dropping out at the same time.
They are not on the same bank.
The layout is 123 in the back and 456 in the front.
I decided to current ramp the coils from the underhood fuse box, because it was easy, and I could see all six coils were being controlled during the miss.
Considering it runs perfectly for several minutes, I decided no to perform a relative compression test.
I decided to investigate the code set criteria for the p0355 and make a plan to test the crank sensor.
During my research and set up, the battery died in the Acura, and naturaly, the codes disappeared. (I was then informed that they battery had died several times and that part of the reason for the visit to the shop was battery replacement.)
I thought this would be a good opportunity to see if the CKP code set first, or the misfire codes.
Once jump started, it ran well, then didn't (as expected), and the first codes to return were p0302 & p0306.
I scoped the CKP any way and found the pattern to look pretty much as I would expect.
With CKP looking ok for now at not coding, and coil control not dropping off, I began to consider a running in cylinder test, thinking of some GMs I have seen with failing lifters that would result in uneven compression once running.
Not wanting to go that deep just yet, and remembering the CKP code that was in the computer before the battery died, I decided to poke around the scan tool data and functions related to the crank sensor.
There was an option to clear the crank pattern and another to relearn the pattern.
I decided to give it a go, not really expecting any results.
I was very surprised when the misfires did not return!
My feeling is that the weak battery repeatedly dying and being jump started some how was responsible for the crank pattern either being lost or learned incorrectly.
I'll admit, I got lucky. This could have gone down the rabbit hole quickly.
I'm looking forward to opinions from the community, thanks for taking the time to read my post.
"Ground cannot be checked with a 10mm socket"
