I have a 1994 blazer with a 4.3 vortec, new plugs, new wires, new distributor cap, ran fine until last week, I put it in drive and it runs rough, it starts fine and runs fine at idle. I pulled the codes and got a 66, which shows the ecm in the manual that came with my code reader, your codes interpret as posted on your site as 3-2 control solenoid which I would guess is a transmission code? Help

 

Have you checked your tranny fluid? What does it look like?

 

tranny rebuilt less than 100 miles ago, fluid fine, no discoloring

 

My first guess would be that you have a vacuum leak and/or an EGR problem.

 

Would this cause a code 66?