I had been noticing as we moved into winter that the temp gauge stopped working in my '95 Accord LX. I assumed I needed to change the temp sensor. The heater worked fine, so I didn't really consider the thermostat a suspect.

My wife called me one day from out on the highway and said the car was revving too high at 70 mph...I drove it when she got home, and it seemed fine.

I drove it the last few days, and noticed it was idling too high (1000 rpms). On the highway I noticed what she was talking about, it was running 3200 rpm at 70 mph, not 2800 or so like normal. Seemed the TCC wasn't going into lock like it should. Sometimes it would lock and rpms would drop, only to jump up again.

I also noticed the radiator fan's operation seemed kind of strange, like it was coming on every 30 seconds or so in city driving, only to shut back off almost right away (like less than ten seconds)...

Fuel mileage has been lower than normal also. Much lower.

Today I decided to remove the thermostat and have a look, just to rule it out before going farther. As soon as I saw it, it all fell into place.

There is a rubber seal where the thermostat's plunger seats...it had slipped out of place and was caught in the plunger, holding it open slightly. Not enough to cause the heater not to work, but enough to cause the engine to run cold...and keep the idle and mixture in a cold/rich mode, prevent TCC lockup, and cause the fans to short-cycle.

Thought I'd toss it out there as something to check if you have similar symptoms someday...

That's a cheap fix. How often do we have to change the thermostat? I have over 120k miles and still on the original one. I get about 80mph @ 3000rpm.

This OEM 'stat is really well built, and lasted almost 180K, so you've probably got time....;)

Mine is running for 127000 mi and still working, but I should change it soon too. If I pull the hose out when the engine is cold, will there be any coolant? I don't like surprises :)

Yeah you'll lose about 1.5 qts