Chevrolet Repair: 89 s10 rough idle- hot, egr valve, s10 blazer 4x4

Question
Van - 89' s10 blazer 4x4, v6 4.3

 started going into a looping rough idle when coming to a stop after engine reaching operating temp. - intermittently.   cleaned iac and then
rpl'ed with new, rpl'ed egr valve and then vacum
solenoid, rpl'ed temp sensor, rpl'ed tps.
runs better than ever except when hot and after
driving several miles.
  have opened hood with engine at rough idle - found egr valve to be open and cycling with the looping engine- pulled vacum hose from vacum solenoid egr closed engine returned to norm.
vacum was present at solenoid.--dont know what else would comand vacum solenoid to drive egr open at idle.
 vacum hose's -found no leaks-rpl'ed tbi base gasket as did have leak with problem returning.
no messages from ecm.

Answer
Hi Bill,
You unplugged the EGR, and idle returned to NORMAL? Good deal.
The ECM tells it when to open, due to several inputs. But that EGR valve could also be a backpressure feedback valve, and if the exhaust system is restricted, it might be having an effect on it.  Just a thought.

Vacuum should be present at the feed side of that solenoid, but the solenoid should be closed. I wonder if it is leaking, and the combination of the leak, and the exhaust, or just the leak is opening the egr. Can you unplug the wire to that solenoid and see if it stops opening?
That will probably set a code, and turn the engine light on, but an 89 I believe you can clear without a scan tool, and it might clear itself when the wire is reconnected.
You might just want to replace that solenoid valve.

Van