1967 122S Wagon, B20E, M41, Dual HIF6 carbs, Fuel Pressure Regulator, etc.
one HIF rebuilt, both with new throttle shaft seals. Single-box air filter, Marvel Mystery Oil in the dashpots.

I've had a couple of "cruise control" issues with my car since last week. Mainly in that I don't have cruise control, but the car has been partially driving itself.

The first time it happened, I noticed that the car was not slowing appreciably when I let off the accelerator pedal on the highway. I pulled off at my usual exit and was pulling off to check the setup when the rpms dropped down to normal. The problem didn't return... until this morning. When I was about 5 minutes from work, I felt the car fighting me when I was breaking. At a stoplight in neutral, the car ran up to around 5000 rpms and all the reving and pulling back on the accelerator pedal did very little - dropping me to only 4500 rpms. Fortunately it was a short light.

I left the car in the lot at work and did not get back to it until I was leaving this afternoon. Once the car got going, the engine stayed around 3000 even with the choke off. I got the hood open and confirmed that the linkages were loose and that the choke was operating normally. I reved the engine with the throttle linkage and after a bit the idle dropped to normal. It stuck a bit on the way home, but eventually returned to completely normal operation.

What's going on here? The only real difference lately is that it's gotten and stayed a lot cooler (mid 30s F), maybe the O rings I used for thottleshaft seals are sticking? Maybe MMO is not up to task in Missouri?

I'm planning to lubricate the throttle and linkages with either white lithium grease or silicone spray.

Any thoughts?