1990 Ford Thunderbird SC Questions

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Car will run and then shut down
On start up car idle's at 500 RPMs has miss fire. On acceleration has no power I have to floor it to get up to speed. And trans shifting I'll regular
I spoke to my stepfather who is a master mechanic and been one for 40 years...
He is the one that has done 99% of the work on this. But unable to figure out the problem.
Crate Motor 40k
Rebuilt S/C 10k
All new Main Fuses/Regular fuses
New Fuse Boxes
New Computer
New relays, Sensors, Sending units, Etc.
As he tried to fix the problem, he would replace everything.
New Fuel Pump replaced inside the Fuel Tank.

Car starts and will run great up until it hits running temp...
Then begins to pop, sputter and acts like the timing has been retarded then dies...
Wait 10-15 mins. - Car starts up again and runs great.
We have had the vehicle to 2 different dealers and left for several days each time.
Spark plugs and wires have all been changed and double checked to make sure snug and no shorts.
Any ideas on this?
Does anyone know of a mechanic that specializes in the
90 T-Bird Super Coupe?
Please don't hesitate to ask further questions... This has really been a pain...

This vehicle is in excellent condition. It has a crate motor with approx. 30k on it. The various components have all been replaced; alternator, S/C rebuilt, all sensors, fuses, etc. have all been replaced. It starts and runs great, but then simply dies and will not restart. I have had it to 2 separate dealers and left it with them for days. Neither were able to locate the issue. my mother is the 2nd owner of the car. The original owner had been involved in a front end accident which resulted in replacing the passenger side fender and parts. I have been told that based on that, the front wiring harness could possibly have a short in it? This problem has stumped the best mechanics from both CA and WA states. I know long distance makes it very difficult to figure out, but any thoughts? Any T Bird SC mechanics in Puyallup WA area you are aware of?
Thank you for your time.
I have had this car at 2 dealers, 3 shops and my step father (With 40 years Automotive experience) have all tried to find the problem but so far been unable to.

The engine is a brand new crate motor from Ford. It has about 25k on it. Everything else has been replaced from the supercharger to the plugs. Etc...

The car has always run perfectly.

The general consensus now is that as the car was in a minor fender bender some years ago where the right front fender had been damaged
and replaced that the wiring harness from the engine to the computer might be damaged?

When I say that everything else has been replaced, I mean everything!

The dealers have all had the vehicle in their possession for days on end, hooked up to their computers, and as of yet been unable to figure out the problem.

We are all at a loss. Any ideas?
had just changed the valve cover gasket and replace the throttle with a crown victoria throttle
gas it wants to stop but wants to go when I let off. also I have to hold both break and gas pedals down for it to stop
problems when I push the gas it wants to stop but when I let off it wants to go can anyone help
90 super coupe 115XXX miles. Car just likes to crank And crank.has fuel pressure and after a few second to a few minutes depending on the day of cranking it will finally start. Any idea where to begin will help
this started Sunday, i made it home, but not without having to put the car in neutral at every light ,tap the gas to bring the idle down, but when it got down to what is the new normal 2-3k idle there is a nasty humming vibration like noise, but not as your driving as mentioned...Then, in park when I start the car it reves way above the normal idle RPMs, then fluctuates. this is the same with the electronic connections connected and disconnected from the IAC device on the TB all the while i hear a loud humming noise from the engine.
i have an IAC part on the way, but are there any other ideas, i have heard that is the issue...but am looking for a second opinion...
was told that it was the inter cooler that needs to be sealed correctly or it wont start is this true ive had the car for 2 years fixing it a bit at a time on my own but stuck on this last bit please help
problem started about a week ago and is consistent. Car has 144000 miles.
restart it ,it runs rough for awhile , and then smooths out afer I get moving,also i notest that if i run the ac unit it doesnt start back up rough,what can be the proublem, new o2 sensors airflow sensor i re place idle control please help me here with a few ideals thanks
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