I have a 2012 M37x that continues to produce this code after replacing spark plug and coil. Upon startup I get rough engine idle which then calms down to normal and the engine runs fine. Eventually the check engine light comes on and the scanner consistently shows PO302 misfire cylinder 2. Once I clear the code the rough start goes away and car starts fine for several weeks and then the rough start presents itself again and eventually the check engine light comes back on. Anyone else run into this issue and have an idea as to what the issue might be?

if it consistently steadies out after running for a bit, my first two suspects would be a slightly leaky injector or a very small head gasket leak. Neither one necessarily produces a lot of smoke and both will cause a misfire on startup which clears after the fuel or coolant is ejected.

I was thinking injector as well. Engine has never overheated so would be surprised if head gasket leak. Car has 137k mileage. I’ve taken very good care of the car so not hard miles. Thank you for the feedback.

I have a similar problem but mine is random misfire. I believe that my intake valves have carbon build up which is throwing of my idle. Try using some sea foam fuel system cleaner and see what happens. Good Luck

I thoroughly cleaned both throttle bodies & executed relearn procedure. Read a thread where someone was experiencing my exact issue generally during warmer temps but in colder temps the issue would go away. Which is exactly my experience but recently it started happening in cold weather. I’ll try the sea foam. Appreciate the advice. If that doesn’t solve the issue then I’ll pull the fuel rail & replace the injector.

Any update?

Idling at start up has been normal for the past 3 weeks and just when I think the issue is no longer I had a rough idle upon start. At the time I had just under a 1/4 tank of gas which got me thinking is this a fuel pump issue where it only occurs once my fuel gets at or below a 1/4 tank. I’m going to monitor this to see if the cycle repeats. Still need to add sea foam to see if that helps. But skeptical because I’ve previously tried Lucas fuel treatment as well as chevron Techron fuel system cleaner with no success.

It's not uncommon for fuel pumps to act up when the tank gets low. The motor is cooled by the fuel, so when a motor is fixing to quit, problems often first appear when the fuel level is low.

Update on the misfire. Replaced plenum gasket but didn’t resolve issue. Replaced fuel injector but didn’t resolve issue. While driving in very hot conditions car overheated. It was roughly 1/2 gallon low on radiator fluid. Topped off and ironically the misfire is no longer occurring. It’s been 4 months since the overheat and not one misfire. I don’t understand the correlation between low radiator fluid and a resulting misfire. Maybe no correlation at all. Either way, I’m glad to say the misfire is no longer. The low fluid level goes back to a radiator hose being replaced and upon filling with fluid the system was not bled. After the hose was replaced there was a gurgling noise that sounded like it was coming from inside the dashboard. Since topping off fluid no more gurgling noise.

Now onto a new fix…replacing the rear diff bushing, which started leaking. Crazy that Infiniti’s fix requires replacing the rear subframe.