So I got the blazer last year, and it has always ran rough. It would shake/vibrate roughly at idle, even to the point where you look in the rearview mirror with a cars headlights behind you and it's shaking and the lights look like they are moving all over the place, along with the seats, you can see them shaking too.

Passengers would get in and always say it runs rough and what not. I decided to see if a tune-up would help it. I know blazers are picky and want AC Delco tune-up parts most of the time, but I didn't get it any of those.

I gave it a complete tune-up right before the summer of 2012, and if I remember correctly, when I started it, it ran flawless for about 15 seconds, then it went right back to the rough/shaking/vibrating.

What could this be? It is driving me insane because the shaking and vibrating is making all my squeaky interior parts make noise constantly.

 

Have you cleaned the IAC and throttle body?
What is the fuel pressure...is it steady? Could be the regulator, fuel pump, fuel filter, injector.
What is the condition of the vacuum lines in the engine compartment? Look for a leak.

What plugs are in? What is the gap?

May be the ECM is just not 100%...but will likely require a scan tool to diagnose.

Need alot more details in order to provide any help.

 

I will get back to you once I check all of those. Thanks!