1994 T Bird, 3.8 Auto.
I have been working on a rough idle, at all times. I was about to injector replacement. I decided to give diagnostics one more try. I did have a code 181 and 189. New O2 sensors have been installed.
I found the timing was at 15 degrees advanced, so I reset it to 10 degrees, with the spout removed.
Long story short, it idles smooth as silk. So why did 5 degrees advance make such a difference?