I just bought a 2000 Blazer 4x4 and it has sat for over a year. I did a tune-up ( plugs wires cap pcv valve oil and filter air and fuel filter) it still has a miss! My trans has begun not to shift.. I can manually shift it but it will not down shift by itself.. And while going down the hwy if I try to pass someone it will just putt and not downshift... Any suggestions would be greatly appreciated... Thank you in advance..

 

Mine is a similar problem. Are you sure you gapped all the plugs right? Mine has a blown intake gasket that I have to replace. Are you leaking coolant as well?, it might have something to do with that because they are known to go bad. I would fill it up with coolant and see if it leaks out or if your coolant is already low it may be the issue.

 

Plugs are gapped correct and intake gasket was replaced a couple of months before it was parked... I have checked all fluids and they are all correct... Transmission is my main concern though... Good luck with your issues