Jim, I had the same probleme a few months ago.
I also replaces all sensors with no luck.
Check and adjust your TPS reading, THen check the resistance of your IAC.
Mine was new and it had a bad reading on one side.
Good luck.
I wonder if he still has the Reatta engine. The first pictures are of a Grand National engine. Valve cover hold downs are completly different on the normal Buick engine and the heads are Not interchangeable.
I had a bad connector and a bad IAC. I checked the connector first and replaced it. Then checked the IAC with a voltmeter.
The readings are in the manual. and found one side of the IAC was bad. Replaced with another and all is well.
I just went thru the same problem. Replaced all the sensors and still had the same problem.
!st make sure the TPS is set correct. Then remove the plug form the IAC and check the readings
using a voltmeter. You can find the readings in the manual.
I had a new IAC and half of it was not working. I tested anther and found it to be good.
It solved my problem.
Get a large plastic cup, larger than the filter. Crack the filter loose and then put the cup over it and remove.
The hot oil stays in the cup along with the filter.
Still having idling problems. When the A/C is on the engine idles quite fast, around 1300 to 1400 rpms.
When the air is turned off the idle returns to normal around 750 to 800 rpms.
What sensor controls the idle when the air is turned on and off?
Anyone?