Possible causes for a rough idle
1. IACV problem
2. Bleed Coolant System
3. There is a valve inside your throttle body, that is probably loose so tighten it and it should work.
4. TPS. You have to loosen the two screws that hold on to it and adjust the tps (by tilting until you find a good setting for your throttle body)

I had the same problem and i went through hell.

 

what kind of car is it. if it is a honda and it has a fast idle thermo this would explain it going away once the car heats up and that would be your problem.

 

it's probly just tps sensor...very common thing with tune port or EFI motors of all makes

 

my boy fucked with some screw near the throttle body yesterday and nothing happend. i want to know if the iacv from a 1.5 motor will work on my car(d16z6) i plan on changing that today and will the tps also need to be from the same exact motor?

 

if you iacv was bad you would have a very fast loping idle.

 

ok what it does is it will rev up to about 2g and then drop really fast then it continues on and on. it does it all the time now. so what could it be then?

 

check for spark could be misfiring =\

 

i still say its a the iacv....and as long as its from the same yr. (88-91) (92-95) (96+) then yes the other iacv should work....as long as the bolt holes are the same should be no prob.

 

yes if you havent already done so, pull your intake piping off, and on the inside towards the back (firewall side) there should be a hole going to the iacv wich controls the airflow at idle....stick your finger/thumb/tape...whatever over the hole to block it off and see if it idles smooth like it should...if it does then its the iacv...

P.S. dont be afraid it wont bite you....

but you might get a hickie....

 

Hahahaha