funny rattling sound in d series motor
 

I have an 03 civic lx with 1.7 d17a1 . took to shop because there is a weird noise in the motor. mechanic used a stethoscope and tells me immediately its a rod bearing. makes sense as it rattles only at about 3000 rpm and not on idle. but when unplugged coil packs one at a time while at this rpm to tell which cylinder it never went away . could it be a main bearing. sorry I dont trust alot of mechanics anymore as I'm a truck driver and see how shady and wrong some mechanics can be. any ideas or insight is much appreciated