Warmed up, idling too fast

[GeoHacker]

Has the original thermostat on this car I think, still. That a potential cause of this? No obvious vacuum leaks found yet, though reading through some posts here indicates likely cause.

Update, just took another drive. Started, went to usual 1800. Idle never went down below 1600. Went a mile or two down the road. Idle went up to 2200…cold needle on temp gauge, at C mark.

I stopped at an intersection…soon as temp gauge came up (thermostat opened?) car changed to surging between 1500 and 2000…would go up to 2000, come back down to 1500…go right back up again (every 2-4 seconds) temp gauge too past the middle, too fast.

While at the light initially, the temp gauge was at bottom C…by time across intersection, surging started, gauge went almost to half way instantly…that is not normal for my car for the gauge to go up that far that fast.

Checking for a leak soon as cools back down. Sure hope it isn't that one hose I never could get to to replace, the one on the passenger side of the engine under all the works which kind of seems like you have to take the engine out to get to the clamp up front near the water pump.

r