Sorry I haven't got back to you yet. I did check the upper and lower hoses with my infrared temp gun while the engine showed to be fully warm. The difference between the two hoses was only about ten degrees. I wouldn't think that was enough of a difference to indicate a thermostat problem. I'm going to replace the temp switch and make sure all of the air is out of the cooling system and see if that makes any difference. (I worry about air in the system because all three coolant temp senders are above or at the same level as the top tank of the radiator and are located on the backside of the engine.)
At this point, just as soon as either you or I figure out what's causing this problem I will make sure you get paid the deposit I have put up for your time. If you can think of anything else that could be causing it to have a very rough or dying idle only after a warm restart, please let me know.
A further note; it seems like this problem occurs most often when the engine is restarted within 20 to 30 minutes after shutting it off fully warm. So far the elapsed time and engine fully warm are about the only common denominators I've been able to pin point that corresponds with this problem.
Other info about this vehicle;
Mileage about 219,000
Reman long block installed around 125,000
Trans rebuilt around 150,000
I took possession 171,000 with blown head gasket
Heads resurfaced and pressure tested, new head gaskets, timing belt, timing belt tensioner and idlers, water pump, and thermostat all installed @ 171,000.
New engine control wiring harness installed around 179,000.
Valve clearance re-shimmed around 204,000
Engine driven fan removed and thermostat controlled electric fan installed around 217,000
218,000 new valve cover gaskets, 6 reman injectors and 6 spark plugs installed, first of three coolant senders replaced, new fan idler shaft(also known as water pump bracket) installed.
Now after seeing some of the history, it might help you to know, this problem has been evident for more that 2 years although not as severe as it has become just after this last round of repairs. Before it would want to run rough for 20 - 30 seconds when restarted warm but it would very seldom die. Now it will idle so rough that the idle will drop to below 500 rpm in neutral and then die if I don't immediately rev it up to about 1500 - 2000 rpm. If I hold it at that rpm for 20 - 30 seconds, then I can let off and it will return to a normal idle again.
I hope I've given you enough information this time to get a clearer picture of what's happening. I know it can be hard to determine the problem without actually seeing the vehicle or this type of problem on a similar vehicle.
I look forward to your next suggestion.
PS: I've upped the offer to $25.00