I have a 92 civic hatch with a d16z6 swap. Anytime I have the heat on, it will jump about 500-700 rpm's when I'm at a red light or sitting still. It used to do it all the time, but I cleaned the iacv and adjusted the fitv. It stopped the idle jump, but when I did this, I never used the heat. I just now noticed it b/c its cold out and I use the heat.

It rarely does it with out the heat being on. Also I'm throwing a code 10(intake air temp sensor) I didn't know if this is a factor or the problem.

If anyone has any help, it would be greatly appreciated. Thanks.

 

Definitely fix the code 10 problem. Also check the coolant level and bleed the cooling system (may have some air trapped in it).