so i have a jdm second gen b16a and the idle is wierd. when cold its between 1500-2000, when it warms up it sits around 1000-1100. Some times i dont even have to accelerate to go into gear, just need to release the clutch and im off. I also noticed that the lower rad hose is ice cold and the upper is HOT. I have heat in the car, the temp gauge reads normal. I have tried bleeding the cooling system for air bubbles but doesnt change anything. The water pump, timing belt and tensioner pulleys have been replaced recently. I'm not loosing any coolant and cant seem to figure this out. i also cleaned and tightened the FITV as suggested by other posts. Any help would be appreciated, im familiar with cars in general but this is my first Honda and previous owner did the swap.

 

Thermostat?

 

If the thermostat is done would there be no heat in the car? I thought that was the first sign, but i'm no mechanic so i could be wrong. Is there any preffered thermostat i should get for the second gen OBD1 b16a?

 

Your idle and coolant problem seem like two different problems. fix the idle first
Then if after running your car for 30 minutes, and that hose is still cold it could be clogged or you could have the thermostat installed the wrong way. The way i used to check if it was my thermostat was take it out, put the hose back on and run the car, does the hose get warm?
Make sure the "pin" is upward in the designated spot on the thermostate housing.

 

bad thermostat and/or a partially clogged radiator....

its possible that this cooling issue you have may relate to your idling issue... it definitely doesnt help the problem.. the cooling system has a lot to do with the engine idle speed

before anything - check for vacuum leaks - this is a common problem that will cause a high idle, and usually a cheap and easy fix..

the intake air control valve (IACV) plays a big role in the engine idle speed and often gets filthy dirty with carbon. this causes the valve to not open or close all the way or at all and will affect your idle behavior dramatically - this is a common issue with hondas and its an easy fix....either clean it or simply replace it. (assuming its getting power)

the IACV has 2 coolant lines - coolant going in and coolant coming out....now the coolant temperature is what the IACV uses to control the engine idle speed. if the coolant temp is low then the idle will be higher than normal to help warm up the motor, if the coolant temp is hot then the IACV will allow a lower, normal idle speed. very simple.

if there is an issue with your cooling system its very possible that can relate to your idle issue....it sounds like you have a circulation problem, poor coolant circulation can cause the IACV to not work properly...

my advice would be to resolve your cooling issue, (seems like a radiator and a thermostat will cure it, but make sure you confirm this) and clean or replace your IACV and take it from there....
good luck bud!