I know this has been brought up before but this was not answered. I have been having a small issue of my blazer missing, bucking , a little at 70 MPH (2k RPM). It only does it for a bit and sorts out after a couple time. I did a seafoam treatment and it helped a lot. It started again the last couple of days. Yesterday I put 93 octane gas in it and noticed this morning that it ran great. Very smooth and not missing or bucking. Could it be that I still have build up on the combustion side of my engine? This engine only has about 60-70 K on it and was crazy clean on the inside. I may do another seafoam treatment and see if that helps. I have not pulled codes. I could stop by AutoZone and do that too.

 

It could be moisture built up inside your distributor cap that evaporates once it's warm. Do you ever have trouble starting it after a cold, but humid night?

 

It starts on first bump. Especially after the seafoam in the tank. I will see if it does it on the way home today. It is about 50 today after being below 30 for the last few days.

 

Try replacing your cap, rotor and fuel filter...then do a fuel pressure test just to make sure that your pump isnt taking an early vacation.