LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Surging Idle

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Old Apr 22, 2009 | 06:09 PM
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Default Surging Idle

Just fixed cracked heads on a 93 lt1 that i bought. I was wondering if anyone had a vacuum hose routing on not only the emissions side but I noticed that there were two hoses running to the lower front of the motor not sure what they are supposed to go to. The car has a surging idle when the car gets warmed up at a stoplight, I think it is either a vacuum leak or vacuum hose going to the wrong port. Any sugestions?
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Old Apr 22, 2009 | 06:15 PM
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Originally Posted by 93' LT1
Just fixed cracked heads on a 93 lt1 that i bought. I was wondering if anyone had a vacuum hose routing on not only the emissions side but I noticed that there were two hoses running to the lower front of the motor not sure what they are supposed to go to. The car has a surging idle when the car gets warmed up at a stoplight, I think it is either a vacuum leak or vacuum hose going to the wrong port. Any sugestions?
Evap diagram:
http://shbox.com/1/1995_evap.jpg

AIR & EGR ('93):
http://shbox.com/1/1993_air_egr.jpg
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Old Apr 22, 2009 | 06:21 PM
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thanks that helps a lot. You wouldnt happen to know where the vacuum hoses that come from the front of the engine would go or what they are for?
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Old Apr 22, 2009 | 06:22 PM
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Originally Posted by 93' LT1
thanks that helps a lot. You wouldnt happen to know where the vacuum hoses that come from the front of the engine would go or what they are for?
Does it look like the bottom three squares in this diagram?

http://shbox.com/1/air_pump_recall.jpg

Also, check your intake elbow for cracks.
Same with the rubber PCV hoses:

http://shbox.com/1/pcv_pipe.jpg
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Old Apr 22, 2009 | 06:27 PM
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Not really the only one that looked similar was the bottom right
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Old Apr 22, 2009 | 06:29 PM
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When i put it back together i bought a new pcv hose which was just a small piece of hose shaped like U
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Old Apr 22, 2009 | 06:49 PM
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There is one small hose with a couple of check valves in it that goes to the bottom of the engine, then there is another small one that runs behind the water pump and looks like it connects onto the timing cover
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Old Apr 22, 2009 | 07:00 PM
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Originally Posted by 93' LT1
There is one small hose with a couple of check valves in it that goes to the bottom of the engine, then there is another small one that runs behind the water pump and looks like it connects onto the timing cover
These? These are optispark venting hoses, but your '93 wasn't equiped with them. But if the previous owner bought a MSD cap and rotor, then you'll likely have them.

http://shbox.com/ci/opti_vent.jpg
http://shbox.com/1/opti_vacuum_harness.jpg
http://shbox.com/1/opti_vacuum_hose.jpg
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Old Apr 22, 2009 | 07:53 PM
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Yeah that is exactly it, like i said just bought the car in december and have no idea what has been done or changed on it. the only difference is that i dont have a place to connect that hose to me air intake hose.
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Old Apr 23, 2009 | 03:38 PM
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Originally Posted by 93' LT1
Yeah that is exactly it, like i said just bought the car in december and have no idea what has been done or changed on it. the only difference is that i dont have a place to connect that hose to me air intake hose.
You mean the little blue plastic elbow that plugs into a little hose in the big black intake elbow? All you have to do is drill a little hole in the elbow.
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