1993 del sol si. D16z6. The other day I had my car idling for a while and it started pissing coolant and smoking. Shut it off and left it for a few hours. Drove it home, it did the same thing. The next day I had to drive it to work (it didn't start pissing coolant till it got hot, and was overheating.) but when I drove it to work the idle was bouncing like crazy and not randomly, it goes to 2k than drops, back to 2k than drops, over and over again. It's super annoying but doesn't seem to effect anything else. I've fixed the coolant issue, the hose between the heater control valve and the engine had a crack so I replaced it. However, the car still has the idle issue. Any ideas?

 

Try cleaning your fast idle thermo valve and your IACV. I had same issue my fitv backed out completly and i took it off screwed it in no more rev jump.

 

Did you bleed the coolant sys AFTER you replaced the hose ?

 

Have u also replaced the thermostat? Maybe u might have a blown cylinder head gasket

 

If it's a gradual rise to 2k, then a sudden drop to proper idle, that points strongly to your IACV. Bleed your coolant properly, and if that doesn't solve the problem, remove and clean your IACV. If that still doesn't solve it, replace the IACV with a new factory unit.

 

Read B Swapped93 - You have a classic case of air in your coolant system. There are a bunch of ways to resolve this but the most common is to park you car on a hill as steep as you can find with the front bumper pointed up. Let the car cool down a bit so you can get the radiator cap off and then fill the radiator up with coolant all the way and let the car idle until the fan comes on twice...(usually about 15 minutes)
Any air that might be trapped, usually finds it way out. There's also a bleeder valve on the water inlet neck on some engines, open that also if you have one. Just don't forget to close it when you're done. Make sure its all filled up with coolant, close the radiator cap, and bleeder valve and see if the problem remains. If so...let me know and try to address it. Good luck.