Quote Originally Posted by 383 chev
i just picked up a 94 chevy 2500 and at an idle it revs up and down and sometimes when i give it gas it has a lean bog the guy i just got it from had true dual exhaust put on and never had the O2 sensor put into the pipe could this be the problem. or any other suggestions
its a commen problem with the chev TBI motors. check to see if your EGR valve on the intake is plugged with carbon and make sure it works properly, check the base gasket between the throttle body and intake for a vaccume leak or any vaccume leak with the hoses. but the O2 sensor doesn't effect your idle really but it will with the MPG if your service engine soon light is on. but 80 percent of the time its a vaccume leak a quick way to check the base gasket is have the truck running use a hand held propane torche that you use for soldering house hold copper pipes together an turn the gas on a little bit an touch the tip around the base of the throttle body and see if the idle smooths out instead of up down up down you should find out right when you start poking the tip around front back an sides of the base if it don't change check for bad vaccume hoses and the EGR valve a spray can of carb cleaner(gum out) cleans out the carbon pretty good might need a pick to to loosen up the hardend carbon.