92 Ford Taurus Lean rough Idle after Hot restart

I need any imput anyone might have on this problem my fathers car has got. Its a 92 Ford Taurus 4dr. 3.OL single overhead cam Auto Trans with 168,800 miles and is in great condition.
The car has a lean rough idle after the engine is restarted when it is hot.Idle speed drops to around 400 rpms check engine light comes on and it stalls out sometimes. Makes no difference whether its in Park,Drive,Reverse, or nuetral. And it always starts right back up when it stalls.When driving the car at any speeds it runs great.This problem is only after the engine is restarted when completly warmed up.The car runs great when driven for the first time of the day,you can drive for hours and stop 100 times at red lights and it idles normal with no check engine light.But stop at a store and turn it off for a couple minutes and then when its restarted, back to very low rough lean idle before you can even get it out of park,and stays that way until you let it completely cool down again. Codes stored are 172 and 176 always lean.Repairs tryed so far.New plugs and wires, checked for vacoum leak,checked pcv valve,fuel system cleaner 3 tank fulls in a row.checked EGR valve.Checked and cleaned MAF sensor.Had him unhook the MAF sensor when it was idling rough and didnt change anything.Also had him unhook the ECT coolant Temp. sensor and when he did the rpms came up to around 1000 and it smoothed out,the rad. fan runs all the time when the ECT is unhooked.Replaced the ECT sensor with a new one from Napa,but did not fix the problem.Told him to unhook the ECT sensor and Drive the car a couple days. The car ran great no more lean idle or lean codes stored. I am thinking he got a bad ECT sensor or needs to buy one at the ford dealer.I`m Stumped because it only idles bad after a hot restart. I`ve been a Honda auto tech for over 20 years and am trying to help my father in his 60s find out what is wrong with his car (over the phone),because he lives 1,400 niles away and is on fixed income.

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