p0301 missfire issue, UPDATE

[JSpecV03]

ok so i recently had some issues with my car that i worked out. i had to replace my pre cat so i threw some 4-2-1 headers on my car, and installed a hi-flow cat BEHIND my downstream o2. the upstream is on the header itself. my car is throwing a p0420 for cataylist low effeiency. i clear the code and every 3rd drive cycle the MIL (CEL) comes back on. so i understand whats going on here. i used an anti folwer on my downstream o2

but the main problem im having here is a p0301 cycl. 1 missfire. i check my plugs and they are find with a nominal gap of 1.1mm (0.043in). i swaped 1 and 3 coil packs around and the problem is still in no 1. at WOT around 4-5k rpm it feels like the car is struggling for power, and bucks a little bit. then a flasing mil comes on for a min and then goes off. ive cycled 2 bottles of fuel injector cleaner through it and no change. so i think my injector is shot but im still not sure if thats it.

so is there anyway that the p0420 code is affecting this po301 missfire in cycl. 1? or are the 2 totally unrelated?
help would be great guys

[05OCsrt-4]

either change your plugs, or its a fuel delivery problem, possibly injectors
and most likily the p0420 isn't causing your p0301

[JSpecV03]

ok cuz thats what i was thinking its my injectors.

[Buster]

I had the same problem in my spec v, swap cyl 1 and cyl 2 injectors and see if the problem moves the cyl 2. if it does you found your problem.

[HQuakers]

Like everyone said, swap out injectors, plugs, plug wires to another cylinder and see if it changes. Check to see if the connections are all tight.

[JSpecV03]

I had the same problem in my spec v, swap cyl 1 and cyl 2 injectors and see if the problem moves the cyl 2. if it does you found your problem.

what did you do to fix, just swap around your injectors?

[Buster]

my misfire was in #4 so I took #3 and #4 and swapped them and the misfire moved to #3. Its pretty simple, while You have the intake mani off check to see if all your butterfly screws are still in or loctite them.

[JSpecV03]

my misfire was in #4 so I took #3 and #4 and swapped them and the misfire moved to #3. Its pretty simple, while You have the intake mani off check to see if all your butterfly screws are still in or loctite them.

i pulled the intake collector off a few weeks ago, when my car was running ****ty and i found the no. 4 cycl. had its valve and screws missing. so i sent the car off to nissan and they did a inspection on everything and put it all back together. i swaped the coils around, i even swapped injectors around, i performed a power balance test and it came back ok,
so im wandering if now its an ignition problem, or worse case senario something internal.

[JSpecV03]

bump for update.

[cburwell]

The valve and the screws were missing on cylinder 4 and Nissan didn't replace your engine? EEK!

Have you done what people have suggested about swapping the injectors? If you put the cylinder 1 injector to cylinder 2 and the misfire appears on cylinder 2, then you can be fairly certain that it is the injector. If that is the case, then hop on the Sentra forums and try to find someone with a set of stock injectors.

[JSpecV03]

The valve and the screws were missing on cylinder 4 and Nissan didn't replace your engine? EEK!

Have you done what people have suggested about swapping the injectors? If you put the cylinder 1 injector to cylinder 2 and the misfire appears on cylinder 2, then you can be fairly certain that it is the injector. If that is the case, then hop on the Sentra forums and try to find someone with a set of stock injectors.

the engine itself wasnt damaged to the point that i needed to replace it. besdies im outa warrenty anyway and dont have like 5 k laying around for a new motor. but its my cycl 1 thats missfiring.
i tried the injector swap and i got nothing. its still missing on cycl 1.
i think it might be an ignition related issue