Ok I have a 97 Blazer that runs great then out of the blue it will start running rough like a misfire and idling rough and no check engine light comes on. If i leave it shut off for awhile and go back out and start it it runs perfect again. So idont even know where to start any suggestions?

 

Doe it ever happen before you get up to temp.. ot totally random?
Have the codes read, anyway. If there are some, post the code not the definition.

Check your pcv valve.

 

It seem to do it when it reaches operating temp. I havnt got a code I asked autozone if they could check it for me but I was told if the check engine light doesnt come on they couldnt check so I dont know what to do.

 

ok got the codes P0300 and P0340

 

P030x - Random/Multiple Cylinder Misfire Detected

P0340 - Camshaft Position Sensor A Circuit (Bank 1 or single sensor)

follow these