I have a 91 Civic with a VTECH B16a engine. The car runs great EXCEPT in warm weather. After driving for a little while the car will not maintain idle in stop and go traffic. This only happens when the weather gets warm. It loves cold, damp air. No one can figure out what is going on. I took it to a Honda speciality shop and they will not work on it because they said it is an "engineered" car and they only work on factory cars.
Any suggestions would be appreciated.

 

Swapped cars can be a real pain because the correct matched parts may not be installed.

General tips are to clean the IACV and make sure cooling system is completely full.

If by "not maintining idle" you mean stalling out in neutral unless you press on the gas, the air valve screw on the throttle body can be opened to increase idle speed. If the screw doesn't do much, remove it completely and check for clogging of the passage behind it.

 

Thank you much for your advice. I have a SKUNK throttle body on the intake manifold. Is the idle screw on the throttlebody?
The car's idle is set very low - about 300rpm. Is that too low?
I just checked the radiator and it was low on coolant. Would that have any effect?
I periodically have been putting in a can of SEAFOAM to a full tank of gas.
I am going to check the idle screw today.
Again, thank you so much.
My car is the Dream Machine and I just posted some photos.

 

I don't know about those throttle bodies but I would think it has an air bypass screw like the stock one. 300 rpm is too low. The idle should be 600 to 750 and in a proper stock setup it is regulated by the computer driving the IACV. A bubble of air in the cooling system causes the idle to vary due to inconsistent readings from the ECT sensor. Also of course there is a risk of overheating, the radiator needs to stay completely full.

 

Thank you again. I am no mechanic but I am going to find that idle screw today. What is the IACV?
Again, I really appreciate your knowledge and input.
Have a great day!