engine noise coming through speakers

I have an aftermarket radio installed with speakers and an amplifier. I'm currently hearing a lot of engine noise going through the speakers. RCA's and power cables are opposite of each other and the amplifier is properly grounded with 4 gauge cable. The amplifier was grounded to bare metal. I also have a capacitor that is also grounded with 4 gauge cable. Any help is appreciated!

the car is a 1993 honda civic dx

Try a ground loop isolator as it's a ground loop that is causing problems, do a search on here for ground loop i found allot on here explaining it, good luck

Do you have a Pioneer Head Unit?

I've been reading up on ground loop isolators and they only "patch" the problem, is there anything i can do with the grounding wires or maybe a new approach to grounding to something to the car? i am an idiot- yes i do the pioneer head unit that i have the is deh-p4200ub. a lot of people comment on the fact that they have bad grounding issues, is there anything i can do to fix it? thank you everyone for your quick responses

awesome, the popping noise is coming through the tweeters, it does not go through the door speakers. can i take a wire connect it to the outer shield of the RCA and the the other end twist it and connect it to ground on the amplifier?

U can try connecting a ground from the amp to the head unit, some RCAs have a small wire in the middle for this, te other option is to earth the sterio at the same point as the amp, from what I read this brings the reference to the same point so there is no voltage change, if I'm wrong pls correct mr ad I'm new to this also :)

It really needs to be done behind the radio.  If you do it at the amp, you will create a ground loop.  The radio is what is supposed to supply ground to the amp.  If you ground the amp end, it will help some, but will not eliminate the noise.

so by attaching wire to both parts of the RCA's and then the end back to the body of the radio, then any noise should be eliminated?