Hello Volvo Friends,
This problem just started during the last cold snap (below 30F for a few weeks). Car has been running fine since the summer. After a cold start, the engine idle drops to near stall speed when I push on the accelerator. It stays at this very slow (below idle) speed (sometimes stalls) for a few seconds. It eventually comes back up after a few pops from under the hood if I keep the accelerator to the floor. If it stalls, it starts up right away and is fine until it drops to the below idle speed again. This drop off repeats intermittently until I can get onto the freeway where it is just fine. I opened up the idle adjusting valve by Counterclockwise turning the idle knob. This helped a little but now my gas mileage has gone way down (with more power) and it still occasionally drops to below idle, even when running smoothly on the interstate for an hour.

Also noticed that the idle cycles up and down now, rather than just smooth idle like it used to be.

Thought it would go away during the recent thaw at 54F but seems to still be with me, although not as bad.

Temperature sensor?

Background: 170k, 245, new bosch cap, rotor, ignition wires, fuel filter, bypassed fuel pump relay (both fuel pumps hot-wired off the battery through a dedicated manual switch and fuse), use high octane gas, new timing belt.

Thanks for your thoughts.