Misfiring while idling

teemoney

teemoney

Member
Location
Toronto, Canada
Car
2007 Infiniti fx35
Notced that when i come to a stop and my FX is idlling it is misfiring. Recently changed the plugs to iridium, put on a CAI, put in a MD spacer and also cleaned the throttle body and MAf. Those things were done months ago but just yesterday and today i noticed the problem. She drives fine but if i excelerate hard i can hear and feel the FX sputtering a little then it will catch and drive fine. For some reason i am thinking it's a bad plug even though i just put brand new ones in. There is no check enginge light and the rpms don't really move even though i can feel the rough idle through my seat. Any ideas what could be causing the issue. Thank in advance
 
It might be a bad motor mount. I felt vibrations inside the cabin also and I thought it was a bad plug but then I found out that my drivers side motor mount was broken in 3 pieces lol.
 
Well the vibration is not always there, plus i can hear misfiring when i take off fast. I will have my cousin take a look after work. Any other gueses
 
Could be a bad coil. Also, when you changed your plugs, did you notice any oil in the well? That would cause misfire as well even with new plugs.

Sent from my DNA
 
Well the plugs were changed over 6000 Miles ago. I asked the mechanic if there was oil and he said no. They also messed up 3 of my coils, all on the drivers side and they were replaced with new ones. The misfiring just started yesterday

---------- Post added at 10:48 AM ---------- Previous post was at 08:36 AM ----------

Well i just took her for a ride during my lunch and now the check engine light is on and she won't idle uner 1000 rpm. So i will be going by my cousins to see what the code is.
 
If they messed up a fourth one would it not show right away. It's been a good 4 months since the mechanic touched it

---------- Post added at 02:30 PM ---------- Previous post was at 12:19 PM ----------

Quick question. On my way to my cousins to get the codes and no more misfiring or sputtering. It idles a tiny but high and the engine light is still on. If i had a bad coil or plug would the probably go away and just leave the engine light on? Seems to be driving great and no loss of power
 
Well i changed the cai/plenum spacer months ago with no issues. Weird thing is i re-tightened the gas cap when i left work and drove off and the misfire stopped. The idle was still a little high and the engine light was on. Went to my cousins and he plugged in a scanner and when we turned the ignition on the engine light didn't come on and we didn't reset it. When i drove it all was well, no engine light, no misfiring and no high idle. So any chance of it being a bad coil or plug that was causing the issue? Just hope it doesn't come back
 
I know, i can't figure it out. I know a loose gas cap can cause the engine light to come on but it shouldn't misfire. I will keep my cousins scanner in my FX in case it happens again.I assume that when you have a bad coil or plug the problem wouldn't just go away so i'm just hoping all is well now
 
So the problem came back but this time i was able to pull the code. P0301. So this means cylinder 1 is misfiring. Which coil pack is cylinder 1. I changed all 3 coil packs on the drivers side already so i hope it's not one of them
 
So i hear it could also be a intake issue. I have a LMS intake with the k&n cone. I was wondering if coil 1 was bad wouldn't it die the first time i was having issues and not last another week
 
I doubt its an intake issue. Although I will gladly take that LMS tube off you, if you really are nervous about it...:rotfl:

Coilpacks can have intermittent problems, its not an on/off type failure.

I would recommend inspecting that coilpack and sparkplug before trying anything else. Once you replace those two items, do the pedal dance, and go from there.
 
So if it is the coil, can i just replace the one or should i change all 3 of the old ones. The only thing that sucks is i won't be able to fix the problem until this weekend, so i guess i'll have to drive with a bad coil for a few more days
 
You can replace just one coil. They really don't need to be a matched set or anything like that. The misfire isn't going to hurt anything, just don't get on it until you can fix it. To test and make sure it's the coil, swap coils and see if the misfire moves. If you swap coils and cylinder 1 is still misfiring, it's not the coil. At that point check the plugs.

Doesn't sound like an intake issue or vacuum leak since it's localized. Good luck.
 
Check the wires by the exhaust manifold, sometimes they can melt and cause electricity leakage. Check up under the edges of the intake plenum at the fuel injector harness. See if there is any damage to the injector harness, causing wires to randomly touch..
 
Thanks you guys for the help. I have no choice but to drive it till the weekend cause of my job. I will check everything emntioned. Hope it's just a coil as that's a pretty easy fix. I will swap coils and scan it again to see if the code changes. Just don't like driving her like this
 
Even if the misfire happens again after you change the coil no big deal. (Coils are only like $50) Check the ECU and then check what I suggested!
 
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