It has been 6 months. I have had a diagnostic at a dealership = replace IMRC motors, it is not an electrical, vacuum or solenoid issue. I have done that. I have blown out the vacuum lines = they are not blocked. The truck runs well with low idle at 1000 rpm that is stable.

It would seem to me that the computer simply does not get a signal that the valves are closed = "they are open but should not be = 1537, 1538.

My inspection has long since lapsed and it cannot pass with these codes.

What next?

 

The codes 1537/1538 indicate they are vacuum operated as opposed to electric motor driven.
They are normally closed until a larger amount of throttle is applied.
The codes come about when the 'switches' do not match the PCM for operation.
Did you put any pressure against the vacuum actuators and damage them?
Try a hand vacuum pump on the actuators to see if you can close them.
The switches are telling the PCM the runners are open as they should do according to the codes.
Your issue is with vacuum application to close them or they are stuck in the open position.
It's should be simple to see the problem with a hand pump and a vacuum gage to tell you what is or is not going on.
Is there vacuum at the intake manifold source, at idle?
You mention idle of 1000 rpm. It should be closer to 750..
Look for either a stuck IAC or an intake air leak.
Either one could affect the intake runner issue.
Your just overlooking something.
Good luck.

 

Thanks for your input. The valve stems move. The old motors both hold vacuum and the springs seem strong. However, I did replace them as I had been told that was what was needed, and that vacuum was not an issue.

I will get a vacuum pump and gage and see what I can learn.

Also, wouldn't a stuck IAC intake air leak give a code?

And, I love bluegrass!

 

Intake air leaks often cause 170 to 175 codes from fuel tables shifted out of range. This is reported by the OX sensors as the only way the system has to report the issue. If they are not yet out of range, no codes.
Yes yes to BG, Dan Paisley and local band Lyken Valley on Jan 21, a sat. nite here locally..
Just diagnos the operation and i'm sure you will see the cause, and don't use any positive pressure in a vacuum system.
Good luck.

 

I had one this last summer doing this. I had to dis-assemble the intake and "free" the shafts, they were stuck