I have a 2000 blazer. Whenever I go up a large hill and it shifts into overdrive my check engine light flashes and remains on. After I turn it on and off several times the light goes out. I had the memory checked and it comes up random cylinder misfire. I have replaced the plugs, wires, cap, rotor, distributor, ignition module and coil. The problem seems to be getting worse. It only seems to happen when it shifts down into overdrive and taxes the engine.
Any help would be much appreciated!!

 

I had the same problem last year and it turned out to be one of the new plugs I had fitted had broken down. So I changed them all again and greased the lead caps before replacing the HT leads and that sorted out the misfire for me.

 

delco plugs only, i think platinums are recommended, the parts store should be able to tell you what went in factory. When you got the new distributor did the timing get set correctly? only way to do it is with the proper scanner.