Hey guys. Recently I’ve been having issues trying to diagnose what feels like random jolting while sitting at a stop light in drive and also in park. Rpms fluctuate ever so slightly when this happens. For context g37 sedan recently got a new engine put In. I believed it was low on transmission fluid before this so I added some and did the whole procedure of letting it get to operating temp and draining any excess hoping that would solve my issue. After doing so I’m still having these issues. I also get the occasional rough shift or stutter when driving. Transmission has about 180k miles. New engine is at about 120k. New engine and transmission mounts were installed when the engine was put in. Also did gallery gaskets. Spark plugs. Water pump. Thermostat. Serpentine belt. What could this be? Has anyone else experienced something similar?

 

Mine was doing the same but I am 6mt. Eventually got worse and threw a p0302 code on cylinder 1. Pulled the plug and coilpack, but everything looked ok. Went ahead and ordered 6 new plugs and z1 coils since they have 66 and 166k respectively. Hopefully this fixes it for me.

Scan your car.

 

It used to have a cylinder 3 misfire code not too long ago. Swapped the coil and plug to a different cylinder and the code went away. The other day I was scanning it just to see if a code would pop up without a CEL and it had a cylinder 1 misfire code briefly then it was gone. I’m guessing that’s the one I swapped that coil and plug too (I can’t remember too well) I have spare coils so ima put one in and a new spark plug to see if that solves the issue. Back when it was throwing the cylinder 3 misfire code I had oil getting in the spark plugs. Replaced pcv valves and fixed the issue but I’m wondering if maybe that’s cylinder’s spark plug got oil fouled. (It’s either that or a vacuum leak somewhere) I’m going to scan it with a better machine tomorrow and see what I find. Will update with what I find in case it may help you.