I just replaced the ECT in my 84 5.0 convertible. It was running rich, backing and stalling. The code was 21 so i put in a new 1145 Motorcraft with new pigtail supplied. Restarted car and it was idling so low it picked up code 17 RPM below Self test limit. So I reset curb idle and got it back where it should be.

Now I get code 46 Thermactor air is not bypassed. I had replaced all the solenoids, the TAB, TAD, all the vacuum tubing when I got the car around 5 years ago. i have swapped the smog pump more then once including just 2 months ago. the cardones are junk.

I did a quick visual check and the TAB and TAD vacuum lines are intact and not broken or removed. What would cause it to not be bypassed?

I would imagine if the solenoids were bad they would show up during KOEO or KOER. So what should I be looking for?