21k

so the codes came up
p0300 - random missfire detected
p0301 - cyclinder 1 missfire detected
p0302 - cyclinder 2 missfire detected
p0303 - cyclinder 3 missfire detected
p0304 - cyclinder 4 missfire detected

i take my car in for an oil change and tell him about the engine light so he replaces the sparkplugs. the light comes back up a couple days later this time he cleans my injectors and changes some sensor. couple days later comes up again dont have time to take the bus so drive it and it goes off by itself. then comes on the next day and goes off the next and now its on again. what do i do??? car runs fine except sometimes the rpm's drop at a stoplight. should i take it to the dealership? 01 s2000 with used engine in it 30,000 km.

CU03BLKS2K

Don't take it to a dealership. There is a very helpful misfire thread, so try searching. Follow what it says on that thread.