So I have a z6 in my 97 del Sol. Did the obd1 conversion, starts and runs fine. No cel. Whenever my car is warmed up and I'm sitting at idle it does this. I'm guessing it's my IACV, but just wanted other opinions. Also, if I am moving and put the car in neutral, the rpm will drop to 1000, and then up to 1200, the back down again. In the video, I am just sitting in my driveway with the emergency brake engaged, not touching the throttle.

Video:

 

Bleed the cooling system.

 

Will try in the morning, thank you!

 

Also of note, it had a y7 intake manifold and throttle body on it so I bought a z6 intake manifold and throttle body and converted all the sensors to obd1

 

After you follow RonJs advice, if that doesnt solve your problem, sure cleaning the iacv isnt a bad idea, but that may/does require a new gasket. Not a big deal i know, but you might want to set your idle (and throttle cable adjustment) per the FSM, it's common to see that simple procedure balance out idle bounce (not as common as air in the coolant tho, hence RonJ mentioning it first), this can be done without a trip to the dealer/etailer/parts store. It's also quite a simple job.

 

Bled my coolant, still does the same thing. However I noticed it does it ALOT less when it's hot and humid out. Any idea?