ok guys new here and i'm saying thanks ahead of time.
ok here's the problem, had my blazer from new never had a problem until now. so far i have replaced the fuel filter, air filter, plugs ,wires and battery. now the truck starts fine , but when i get to the desired speed and try to hold it there the truck starts to buck on me like a missfire, but when i punch the gas she goes no problem as so as i settle her back down and try to hold a certain speed the bucking starts again. any thoughts??????????????????

 

my only thought is that you have the wires in the wrong firing order but you say it only does it when its at a cnstant speed? that stumps me a lil sorry dude

 

Don't quote me on this, it's just an educated guess but it sounds like maybe a problem with your IAC valve (idle air control). You say it starts fine but does it idle ok? Maybe a vacuum leak. Check for a hissing sound under the hood and try to pin point it. Good luck.

 

Could also be your throttle position sensor

 

ok here ya go guys unplugged the iat (intake air temp)sensor. and it went away totally. ordered a new 1 will take a couple days. cecl engine light came on after the 1st couple miles with out the sensor plugged in. drove it around today for awhile with no sudden surging or bucking. seems like i mat have found the culprit.

 

Great to hear it! That's what this site is all about, learning, assisting & advice.