I bought a used Acura MDX 2012 and it has a P0302 cylinder 2 misfire code (and ABS, VSA system, and trailer assist with it), I already changed the spark plug and the ignition coil. It seemed to go away, but after driving 200 miles it came back.
I don't feel anything off, and when I clear the code it stays off for approx 200 miles, so it's not misfiring often (if it even does).
The fuel injectors are pretty clean I think (for extra I used Lucas fuel treatment a few times).
What else should I check fix?
Thank you!
What else should I check fix?
Everything. Anything that affects combustion can cause a misfire, as simple as a vacuum leak or as serious as bad compression and everything in-between. Live data may shed some light on what's going on if you can capture some for analysis when the problem occurs.
What data doing I try to capture?
Even very basic data like fuel trims may help in diagnosis.
it stays off for approx 200 miles, so it's not misfiring often
the light doesn't come on with the first misfire. The computer sets the light after it's sure it's a regularly occurring problem, and severe enough.
So I had a friend with a MaxiSys running a scan / live data, and a few things caught my attention that might point to something. (Might be an O2 sensor?)
I'm not sure what those codes mean so I'll just list it here;
-MAX EMG SPD - is 0 (the car was in park though)
-Misfire cycle - has a high number
-Misfire cycle B - has a very high number
-HO2S (B1&B2) S2 heater current - is 1.03 and red
Attached are images of the scan:
Any help would greatly be appreciated!! 🙏
Anyone with any advice?
What should I look for now?
You mentioned buying this used, if it was recently it's a shame this problem wasn't detected during the pre-purchase inspection.
In any event, here's information on diagnosing the O2 sensor heater circuit, but I don't think that would cause a misfire:
https://www.motor.com/magazine-summary/diagnosing-o2-sensor-heater-circuit-failures/
There don't appear to be any fuel trims in your photos. Those might indicate a problem with too much or too little fuel being delivered. You' may need to record data for analysis while the problem occurs, and might need a scope since scan tools aren't always fast enough to capture transient events. (Modern cars are complex and all too often the cure for a problem is going to require a professional if simpler approaches are ineffective.)
Here are some details on misfire detection and analysis that may be informative:
https://www.tomorrowstechnician.com/intermittent-engine-misfire-analysis/
https://www.underhoodservice.com/tech-feature-courage-under-misfire/