Engine Performance problem
1993 Chevy S-10 6 cyl Two Wheel Drive Automatic 140000 miles
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my truck has been idleing rough for about a month now. it has gotten progressivly worse. it used to run rough only when the a/c was on but we replaced the idle control and the problem was solved for about 4 months. here's the first problem- now it runs very rough when i am stopped or with no foot on the gas at idle speed. almost stalls when you come to an adrupt stop. when you do a steady speed the truck runs perfect. second problem is if the a/c is on,still runs rough but the a/c will quit blowing completly when you try to pass someone or stomp the gas, then resume cold when you let off or maintain speed. to let you know something else-the truck has ALWAYS had blue smoke on start up. the temp gauge reads even and no problem lights come on, no other signs or symptoms that i can make you aware of. the truck runs the same rain or shine, hot or cold weather.

You have a vacuum leak in the A/C vacuum supply line! This is the black line that goes thru the firewall, trace it to either the break, or the check valve and reserve tank, that could be cracked. Fix the vacuum leak and both a/c and idle will improve, the blue smoke is burning oil. if only at startup, it's probably valve stem seals.