Chrushev

I replaced my spark plug for identical ones that were in it (NGK platinum). Those were put in by a shop about 30k miles earlier, and they were not gapped properly (were at default 0.035 instead of 2003 ES's needed 0.039 - 0.043). So the new ones I gapped at 0.040.

When the car is cold and I start it, it vibrates (like if I leave my hood open you can see a visible shake of it). the RPM is solid the entire time (albeit starts at higher than normal idle and lowers down as the car warms up, but the needle doesnt jump). Once the car warms up the vibration is gone and idle is fine at around 0.75k RPM, again, solid, no jumps.

Can this be misfiring? Or is misfiring always associated with jumping RPM needle? Does 2003 Lancer throw a code for misfiring? Can it misfire only when cold?

I did have a battery disconnected so the idle computer got reset and is re-learning. Is it just that? I am torn between putting in old plugs and seeing if it goes away, versus just waiting and giving it a few days to re-learn idle and see what happens then.

Anyone seen something like this?

EDIT: Read somewhere else that Acuras misfire on purpose when cold in order to warm up? Do our cars do the same? Is that what this is? I dont typically just sit and idle and observe, but since I was doing repair work I am a lot more attentive to car's purring to make sure all is well, maybe I just didnt notice before?

Chrushev

Ok, I put in the old plugs and wires, same thing. I think this was probably happening before the change but I just never noticed since I never sat in it cold and observed.