Good morning from East Tennessee! I am brand new to the forum but not brand new to Chevy. I have a "new to me" '95 Blazer 163,000 miles. Me and a friend have been slowly improving its engine performance ... new plugs, new wires, new EGR. However, it is still running rough in idle and in steady speeds like 55-60 on highway. She wants to oscillate and vibrate badly idling at 700 rpm. I am suspecting the MAP sensor or the Idle Air Control valve. Where and which one would you go to first? Or should I be looking at other suspects?

 

Hello and Welcome to the forum! I would start with the IAC valve. That has been the culprit for me in the past. Good luck to you.