Hi,

Quick backstory... I replaced the spark plugs and boots on my M35 3.5L. I got all done and went to start it. It wouldn't start. Took me a min and figured out that I forgot to plug in the passenger side throttle body. Plugged it in and then it started fine... (WHEW). Drove it around the block and it ran great!

The next day went to start it and it started fine but idled rough. Took my son to daycare about 1.5 miles away and it had a small noticeable misfire. Noticed twice that the check engine light flashed. When I got home I checked the codes and I had a P0301 code (Cylinder 1 misfire). Ok, I thought, maybe a bad coil pack. Switched it with #3, a little test drive and still get the same P0301 code. Switched plug boots with cylinder 3, same thing. Switched spark plugs with cylinder 3, same thing.

This is where I am stuck now. My last thought was maybe the injector? or could it be that I need to recalibrate the throttle bodies because I left it unplugged when I tried to start it the first time?

Any advice would be greatly appreciated!

Thank you for your help,
Ben

You should've had a "past" flatline code for the unplugged MAF if it was running long enough to affect anything, either P0102 or P010C. Those usually take about 15 seconds to set, so if you shut the car off before that then there wouldn't be anything stored. Either way, unless the ECM memory got corrupted somehow, that shouldn't cause a misfire. You could try doing an IAVL to recalibrate the MAF's, but I doubt that's your issue. The first thing I'd check is the pigtail and wiring on the #1 connector, seems like that's the only thing you touched which wasn't swapped.

I'm not sure how the MAF would be the issue. Wouldn't it be throwing a MAF code? Just for clarification it was the electronic throttle body that I left unplugged, not the MAF. I suppose it could be dirty but seems weird that it would only misfire on cylinder 1.

Sorry, misread that. But it's the same deal, if it bothered the ECM you would have had a "past" P0233 or P2133. I presume you didn't dislocate much besides the ductwork and TB's, and any kind of leak you could have introduced should be affecting the whole bank. If it isn't a wiring issue and it isn't a rude, unrelated coincidence like an injector failing right after new plugs, then not much else makes sense.

Thanks for your advise. I am going to go out this afternoon and test the plug going to the #1 coil. If it isn't that then it has to be a fuel injector... I don't understand what else it could be. If anyone else has any ideas, please let me know. I will report back once I get to the bottom of this. Thanks

I suppose it *could* be the fuel injector, or more likely a wire to the injector getting damaged while being moved. You should also do the idle air relearn procedure for your throttle bodies as you said. Cyl 1 is the farthest front, correct? If the TB isn't open enough then it could be getting a little starved for air before the other two that are closer to the intake.

Does it run roughly when driving? Or only when down at idle RPM?
Why did you replace your spark plug boots/ignition coil? Were they cracked or had some other problem?
Did you replace the coil with an OEM Nissan one or aftermarket?
Did you replace your spark plugs with OEM NGKs at the standard heat range or with others?