Idle Problems no its not when its cold start.
 

My friend's civic has a rough idle.
Doesnt matter if the car is cold or warmed up. You start it and the car just shakes. Put it in drive with the foot on the brake and the car shakes. its like a really rough idle, the tach isnt fluctuating either. the thing is when you drive you don't feel it anymore.
it has a salvage title. got creamed in the front. engine got replaced.
possibly bad motor mounts?

does it still shake if u rev the engine a bit in park or neutral?
oil and plugs are good?

if you put it in neutral and the car stops shaking, you have a dirty throttle body.

ok ill try that and report back!

ok it doesnt shake when you rev it in park and neutral.

i would say it could possibly be the front motor mount

so what is it?
motor mount or throttle body?

throttle body is much cheaper and easier to try first. but if it is a motor mount, the car would shake while driving too.

tbi is easy to clean. take off intake. clean, replace, be happy. i would check plugs and wires too though.

ok how do i know the wires and plugs are bad?
sorry im totally lost on this part

take out each plug and see if its fouled. like black or something. or if the tip is like melted down. any car manual will have pics of normal and foulded plugs. and it will tell you what causes the type of fouling.
about the wires, look inside and see if you see calcium deposits and rust anywhere.

civics dont have plug wires! coil-on-plug:)

yes they do. the previous gens do. he didn't mention what gen it was...