NO CHECK engine lamp (CEL) glowing running???????
which engine, there are more than one engines, offered on most cars.
that is misfire. and misfire is complex.
there are 50 causes of misfire, on Otto cycle engines (gas)
and more if flooding.
hot or cold engine?
ever do the 60k tune up?
id bet the engine is good, so we can remove 1 of the 3 main causes.
1: bad engine , no
2: bad spark, id bet not if miles is low, is it? below 60k?
3: bad fueling.
that is the proper order,
so if car is tuned up and spark is good.
then it must be fueling. so we connect the scan tool (any Can-bus)
and see DTC errors and it MIL active.
ok its sees misfire P0300s?
if no errors and its misfiring.
we then look at all sensors live with the scan tool.
id bet the engine dont hold closed loop hot, idle , as it must.
screen says, CL = active, or like kind.
if v6, there are 2 banks that must be in closed loop status.
I'll stop here, but will say I have a battery of tests for CL failures.
one is to make sure the 02 sensors work right and that there
are no exhaust manifold cracks near any 02 sensor.
i try to force the engine leaner and righter (tricks) that might
wake up a dead 02,
to see if it swings. (called cross counts)
the causes are many if the sensors are good.
fuel pressure out of spec,
injectors bad, leaking or clogged.
dirty MAF sensor.
ECT stuck at wrong temperature for any reason, 180F or more is good.
and more... ask.