Idle/warm engine issues

[John4574161]

Hello, my son is driving a 1984 633 CSI we restored. Loves it, but some issues.
1. When u first start the car and it is cold, it runs great, can rev motor with no misses. The car runs awhile and once the engine is warm, it starts "loping" at idle and misses when revved up. Have to "feather" the gas when shifting, especially in second gear. If you step on the gas too hard, engine misses. If you "gently" push gas it will slowly climb in RPM's then runs ok at higher RPM's.
We have replaced exhaust and catalytic converter, oxygen sensor, all new and correct vaccum hoses (purchased from Pelican due to tech forum) and a new temp sensor. Have not replaced a temp sensor that sits at front of motor and has a brown and white wire. This "temp sensoe" does not have a long "probe", more of a plug. But, the engine idles higher when you unplug one of the wires, white or brown, does not matter.
When we say we replaced vaccum hoses, this included the 2 large ones that go to the valve cover and the idle control valve.
We need help. What can we next test or replace? Why does the car run so good when cold at first start up, but then idles rough and misses at certain rpms? When it idles "rough" I mean it fluctuates in RPM's. Higher RPM's ok. Always starts good. Idles faster with a temp sensor unplugged that is on the neck of the water pump fitting that goes into a large radiator hose. Thanks!

[phlytrader]

Sounds a lot like a problem I had with a 98 caddy sts. Ended up being a bad spark plug wire.

[SteelGreyE46]

Replace your spark plugs and your spark plug wires and then see how it runs-that should fix your issue since I did not see that you replaced those items:

Cheers!