So heres the deal. My 94 Toyota Pickup is having a strange intermittent issue. Engine will run hot, like the thermostat is stuck periodically. Does not overheat, just runs much closer to the red than usual. Again this only happens sometimes. It is worth noting that it is winter here in Northern Sonoma County, CA, so it may actually get into the red if I were driving around in the summer. I have also not taken it on trips over 30 miles when it was doing this.
When this problem occurs (e.g. the engine has been running hot) and I shut the truck off and say run into the store, then come back to a heat soaked engine it idles very rough when started (like it's missing on one cylinder). Once I put it in gear and start driving the idle smooths out and I have no problems. Problem has been going on for about a week.
Sticking thermostat seems obvious but that does not explain the rough idle on start up. Or does it. If so why?