I have a 89 jimmy w/4.3 . my prob is every once in a while when i start it, it starts real ruff and then wont idle unless the brake pedal is pressed down. the master cylinder & booster were replaced, and i cant find the vacuum line. but when it starts up ruff i can hear a loud sucking, by the drivers side of the dashboard. any insight would be appreciated,thanx

 

Have you tried spraying carb cleaner or unlit propane torch around the intake/vacuum lines to see if the engine noise changes? I have used the propane torch method on many vehicles to find vacuum leaks.

 

ok you have to take your heater controll panel off and on the other side of it there is vacum line harness that clips in on the back of it. it prolly came loose. by heater control panel i mean your controls to change it to heat or A/C or hot or cold and what not. it happended to me but coulnd not find out what it was for a long time.

 

thanx for the advise

i put the newer dash in and didnt totally hook up the back of the heat controls. never thought that would do that

 

glad to help

 

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