LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Oil in vacuum line from vc to tb????

Old Mar 31, 2003 | 03:39 PM
  #1  
QuasarBlue94Z28's Avatar
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From: Torrington, CT 06790
Question Oil in vacuum line from vc to tb????

well i was just tinkering around this afternoon and noticed that around the vacuum line on the passenger side there was some oil and was curious to why it was there and then i checked the line that goes to the throttle body and there was oil there too. so then i took off the elbow and noticed that behind the blades on the throttle body there was what appeared to be black oil. To me, the novice person mechanically, this doesn't seem right so i just wanted to get some feedback from people who really know about this stuff. thanks

tim
Old Mar 31, 2003 | 04:58 PM
  #2  
Injuneer's Avatar
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From: Hell was full so they sent me to NJ
Its not a vacuum line. The purpose of that line is to supply filtered, MAF metered air from a port in front of the throttle body blades, to the passenger side valve cover, where it is pulled through the engine by the vacuum in the PCV valve/system. If your PCV valve plugs up, or if you get excessive blowby on the piston rings, the pressure will build up in the crankcase, and it will blow the vapors, and any entrained oil drops back through the line to the throttle body. It's also conceivable that if your air filter was badly plugged up, you could pull enough vacuum in front of the TB at WOT to develop a vacuum and suck oil through the line into the TB.

It's not unusual to find a little bit of oil in the line. Check the PCV valve. Then with the engine idling, take the oil fill cap off, and feel and listen for "chuffing" of vapors out the fill pipe.
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