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

Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

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Old Jul 23, 2006 | 05:05 PM
  #16  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

ok first what are you talking about you obviously dont know how to read, maybe if you followed along, maybe you would know whats going on... yea... maybe try to pay attention some more.... as for my previous comments they were for injuneer and 95ta to questions they were asking, and did you ever think that maybe i moved from where those pictures were taken guess not lol i dont have time for your stupidity, if you dont have a solution to my problem then dont bother dont you have anything else better to do
Old Jul 24, 2006 | 12:35 AM
  #17  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

anyone else out there with more knowledge know if the pcv system on the valve cover is removed and a breather is put in its place can it cause a vacuum leak?
Old Jul 24, 2006 | 07:03 AM
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

Originally Posted by playa7970
anyone else out there with more knowledge know if the pcv system on the valve cover is removed and a breather is put in its place can it cause a vacuum leak?
No.
Old Jul 24, 2006 | 08:49 AM
  #19  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

It causes the equivalent of a small vacuum leak, since the PCV system is now pulling in air that has not been measured by the MAF sensor.

I'm going to eliminate the photos, because they are obviously causing more problems than helping. I wasn't sure why you wasted the space posting them, but snice they are now causing distractions, I'm deleting them.
Old Jul 24, 2006 | 09:10 AM
  #20  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

*thanks for the fix, hmm is there a alternative solution to put the system back on without having to buy another valve cover, also the intake i have is from a 95 and up and the small port under the TB in the front is plugged

*heres another thing i noticed.. on a cold start up the car measures 10 - 11hg but 10-15 seconds later as soon as the car warms up im back to 7-8 hg of vacuum
Old Jul 24, 2006 | 10:29 AM
  #21  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

The "vacuum leak" caused by a breather is very small, and is not causing your problems.

The vacuum is probably higher at cold start because the idle speed is probably higher at cold start.
Old Jul 24, 2006 | 08:17 PM
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

well i give up, i cant find anything wrong with the car. might possibly be the tune, i called bryan and sent him my data log and hopefully he can help me out ill keep you guys posted
Old Aug 22, 2006 | 11:03 AM
  #23  
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

well im back after a couple weeks and the issue remains and heres what iv done i know the car has no vacuum leaks what so ever so i can safely say its not that i spoke to bryan from pcmforless and he was very helpful what it came down to was for me to buy a vacuum canister and that did improve my vacuum somewhat but no by much now im pulling about 9-12hg so i dont know where to begin now i also spoke to 3 comp cams tech told exactly what i have 383 lt1 and the cam specs and all three of them where like why did you put that into a fuel injection car, with a lobe separation like that the car will have vacuum issues" but i dont know who to believe now is anyone out there running a 107LSA?
Old Aug 27, 2006 | 08:39 AM
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP

Never saw a cam run that had less than 109LSA. Since my cam is more agressive in my 383, I chose a 114LSA to help maintain good vacuum. If I were you, Id'e run a compression test. When you hear air shooting out the intake, you'll know then you have to change cams.
Old Aug 27, 2006 | 09:39 AM
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

I've been fighting a low vac (although not as low as yours) issue and knock as well after a heads/cam install, 236/242 114LSA. Car ran fine for several days with the same tune then all of a sudden started getting all kinds of knock at idle and cruise...now its started at WOT..the max allowed in the tables. AF seems fine so its not a fueling issue and since it ran fine on the tune before I'm at a loss as to what it is.
Maybe the poly mounts or something, I don't know..but I ended up just zeroing out all the knock retard tables in the PCM..effectively turning off the knock sensor since I know it ran fine with no knock with the same spark and fuel table and the car runs great now of course... If the AF is fine then WTH..we didn't have knock sensors 30 years ago and the motors lasted fine...I'm am just tired of trying to figure it out almost to the point where I'll just part out the car if damage happens to the motor cause it ain't worth much now with the diving prices of LT1 cars...
Old Aug 27, 2006 | 09:54 AM
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Re: Low Vacuum, Lots Of Knock, And Spark Retard Dont Forget High Map (log Inside)HELP!...

Join me http://www.camaross.com/forums/showthread.php?t=468086
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