Well, I wanted to get back to everyone on what I found. Today was the day ! It turns out the ECT was faulty. I cannot believe that it made the car run so bad and so hard to start, but that was defenitely it. The car starts right up and runs perfectly now. I wonder if the new thermostat caused the engine to get hotter than it had been in a while and fried the sensor ? Anyway...it was somehow all related. Thank you to everyone who was so helpful and faithful to respond.

Thanks,
Mark

You do have the last year with the degrading engine harness wire insulation. Perhaps the injector wires are shorted inside the harness? Also try cleaning all the ground connections on the inside of both front fenders. Does seem odd though that your engine started running badly after the thermostat was fixed and it then was able to attain the correct running temp?? Try a compression check.

Can you go through the steps you used to change the thermostat? Did you pull anything off? Drain anything through the block drain? Warm it up and burp the system before driving anywhere? Change anything else within the last week?

I know you swapped the AMM, but how does it run with it disconnected?

What is the resistance with the car cold and warmed up on the ECT? Use this link (http://www.swedishbricks.net/700900FAQ/EngineSensors1.html#Diagnosing ECT Failures) (I'm sure there's a section of it in our FAQ, but this was faster for me to find).

I hope you don't take offense at me checking the basics, but I feel like we've heard more about what you've done after the problem arose and I don't believe coincidences happen often.

Also, what do the pins in the AMM look like? One could have been pushed back out of the connector and be making intermittent (or no) contact.

Good Luck!
--
740T and 244DL - Frank the Tank @287K mi. and The Polished Turd @237K mi.

Well unfortunately I am not able to work on my car today and look into some of the suggestions everyone has made. I will be checking the coolant sensor, 02 sensor, Hall sensor and timing on Monday and let you all know what I find. Thank you again for all your help.

Mark

Thank you everyone for replying to my post. No luck so far. Let me answer some questions. First of all, my car is a 1987 760 turbo 4 cylinder. I started using this car about 4 months ago and really went over it well. It has been completely tuned up and anything questionable replaced. the original problem with the car when I bought it was a bad AMM. Anyway...as I said, before the thermo repair the car ran perfectly. The thermo was changed because it is getting cold here and the engine was not coming up to temperature, esp with the heat on. As I expected, the thermostat was broken when I removed it. The car started right up and ran perfectly afterwards. About two hours later when I went to go to the store is when it started acting up. It started right up, but the idle was really high. When I shut it off, it was very hard to re start. When it did start it ran terrible for a while before it cleared up, but the fast idle was still there. I didn't spill any antifreeze during the repair so I am assuming I didn't short anything out. I did not disconnect any wiring, so nothing got mixed up and connected wrong. I haven't checked the coolant sensor yet, only because it is so hard to get to. I do have a new one, so maybe I will try that next. By the way, the car still runs lousy with the AMM disconnected but is a little easier to start. Check engine light is not on and I don't have a code reader...maybe I will have to get one?

Thanks again !

Why did you change the thermostat?

Definitely time to stop slinging parts and start measuring and testing.

We definitely need the year for your car and whether or not it is a turbo or normally aspirated.

Any OBD codes? Is the check engine light on? After you pull the codes you could disconnect the battery for a while to reset the adaptations, which are likely way off right now.

Check to see if the spark is consistent with a cheapie inline spark tester.

See if the injectors fire consistently with a 'noid light you can borrow from Autozone.

Does the car run better if you disconnect the AMM connector (do it when the car is off)?

As others have suggested, the engine coolant temperature sensor and its connector should be checked.

What kind of voltages do you see when you measure the signal coming from the O2 sensor with the car warmed up? Do they fluctuate, or are they pegged at one value (rich or lean)? Does it run differently with the O2 sensor disconnected?

If you pull the vacuum line off the fuel pressure regulator is there gas in that line?

Art may well be on to something regarding an inadvertent swap of the throttle body and idle air valve connectors if the swap did take place.

The 700/900FAQ is a great place to start for diagnostics...

There's going to be a "Eureka" moment on this-- my money is on something being disrupted during your initial work related to the thermostat. Trace your steps!

Good luck!

Did you pour out a little antifreeze before you pulled off the radiator hose? If not, the spilled antifreeze will conduct electricity and must be cleaned off any electrical connector. Especially the ECT sensor.

Klaus
--
My advice is free, so you got what you paid for...

Well since to replace a thermo you dont have to remove anything other then the collent hose it sounds like a fluke and is not related to your repair.
Im going to suggest a few things here without knowing what i really should know so look below for the suggestions and please write back with answers to the followin.

Year?
Engine 4 or 6?
Turbo or Non Turbo?

You said you checked for Vac leaks, did you check the Intake Manifold seal?
Have you checked your fuel pressure or tried another fuel pump?
ECT under the #3-4 intake is it connected, if so you might wanna try a spare.

don't see ECT on your list - did the wire break?

Things like this will move you from part swapping to diagnostics. Sounds like a rich running machine you have there. Or maybe a lean machine. Both stink, just differently. What do the plugs tell you? You sure you didn't swap connectors? You dropped that line in your other thread.

I should bow out here and go back to my 240s. 740s are in another class entirely.
--
Art Benstein near Baltimore

Don't sneeze when someone is cutting your hair.