Most likely causes for rough idling/low speed stalling in 1993 Buick?

What is your question?

I have a 1993 Buick Century 3.3l V6 engine that has erratic idling and stalls at low speed unless I give it about 5% throttle. Car is fine above 15mph. Heat, A/C, and all electronics work. There is no check-engine light and I don't have scanner. So far I have checked all the fluids, changed the air filter, some seafoam in gas-tank, and cleaned the IACV/throttle body. There was a lot of carbon deposit so I'm glad it's clean(er) now, but so far nothing has changed. I suspect one of the following is the issue: IACV is broken Seals on throttle body need replacing Throttle/idling speed is not adjusted properly Throttle Position Sensor is broken Other suggestions? I'd like to know what is most likely the cause and which fixes are the cheapest. The car has little value, I just want to fix the issue instead of throwing money at the problem like what part dealers want. Part stores have been unhelpful and I'd rather fix this on my own if possible. Thank you!

What makes this problem better or worse?

Problem gets worse once engine is warm or goes into gear

How long has your 1993 Buick Century had this problem?

Since purchase (15 days)