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

Vacuum, brake, etc problems

Old Jun 25, 2009 | 07:37 PM
  #16  
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I finally got the valves adjusted, I did "method 3" one cylinder at a time. Afterwards I hooked up the mityvac and got a higher reading but its still eratic not smooth at all. reading is 15-16 bouncing fast. Also the car still wont idle, it idle's for a few mins. then stalls out.

PLEASE HELP,

thanks
Old Jun 26, 2009 | 07:47 AM
  #17  
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Any suggestions???
Old Jun 26, 2009 | 07:41 PM
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How is the idle when it is idling? What rpm? Is it smooth or going up and down?
How does it die? Does it just shut off or does it sputter and that type stuff?
Old Jun 26, 2009 | 08:55 PM
  #19  
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Originally Posted by ACE1252
How is the idle when it is idling? What rpm? Is it smooth or going up and down?
How does it die? Does it just shut off or does it sputter and that type stuff?
when its idling it sounds good, right around 950-1100rpm, its smooth, it sputters tries to keep itself running (rpm's bouncing from very low to idle then it dies)
Old Jun 26, 2009 | 09:28 PM
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Is the fuel pressure constant at idle and when it starts acting up? Any codes?
Old Jun 27, 2009 | 08:53 PM
  #21  
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Im getting a obdI scanner on monday to find out and I have to check the fuel pressure monday also. I'll post again monday night. THANKS ALOT FOR ALL YOUR HELP
Old Jul 1, 2009 | 08:41 AM
  #22  
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I tried to scan the car I was using a snap on scanner for obdI & obdII, I entered the cars info into the scanner plugged it in and got no readings I did exactly what it said to do several times and got nothing.

Also I found a few bad lifters....COMP R's....could this be causing the eratic pressure readings? And the Bad idle?

Also I tried to trace the vaccum hose that goes into the firewall above the A/C box to under the dash and i couldn't find it, woundering if this might have something to do with these problems.
Old Jul 2, 2009 | 07:49 AM
  #23  
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can anyone help out with this... Any help will be appreciated.

Thanks
Old Jul 2, 2009 | 08:44 AM
  #24  
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There is a sticky at the top of this forum about the Comp R's. I don't know if they are your problem, but I personally would not run them. I think I have read that they require 1/8 or 1/4 pre-load(read that sticky to be sure...cause I'm not sure). Much less forgiving on pre-load settings than the stockers.

When I did my cam change, I put in some new stockers. There were nothing wrong with the old ones....I just wanted to put some new ones in there with a new cam.
Old Jul 2, 2009 | 08:56 AM
  #25  
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Originally Posted by ACE1252
There is a sticky at the top of this forum about the Comp R's. I don't know if they are your problem, but I personally would not run them. I think I have read that they require 1/8 or 1/4 pre-load(read that sticky to be sure...cause I'm not sure). Much less forgiving on pre-load settings than the stockers.

When I did my cam change, I put in some new stockers. There were nothing wrong with the old ones....I just wanted to put some new ones in there with a new cam.
ya I read the sticky about the comp r's "after I put them in" haha, I deffinetly have 4 bad lifters, I'm just woundering if that could cause the eratic vaccum reading and/or the bad idle

Also I'm trying to figure out what this small vaccum hose that goes in the firewall above the a/c box goes to?
Old Jul 2, 2009 | 04:48 PM
  #26  
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Erratic valve operation causes erratic vaccum in the intake manifold.

There is a vacuum line that supplies vacuum to the HVAC control panel and flapper doors.

As usual, Shoebox has it covered:

http://shbox.com/1/vac_check_valve.jpg
Old Jul 2, 2009 | 05:21 PM
  #27  
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Originally Posted by Injuneer
Erratic valve operation causes erratic vaccum in the intake manifold.

There is a vacuum line that supplies vacuum to the HVAC control panel and flapper doors.

As usual, Shoebox has it covered:

http://shbox.com/1/vac_check_valve.jpg
Exactly, the one in the picture that says it goes to the mode selector on dash is the one I pulled off, I just dont know where on the dash it connects. Any idea where to look on the dash???

Last edited by asia517; Jul 2, 2009 at 05:32 PM.
Old Jul 3, 2009 | 03:47 PM
  #28  
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FINALLY, I got a good scanner, code 34 map sensor low voltage high vaccum. I put a new map sensor, car idles good, when braking it goes a little low on the idle but doesnt stall, I bleed the brakes good the car stops but not to good. also I found oem lifters on ebay for $119 brand new is this a good price?
Old Jul 3, 2009 | 10:26 PM
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Originally Posted by asia517
Exactly, the one in the picture that says it goes to the mode selector on dash is the one I pulled off, I just dont know where on the dash it connects. Any idea where to look on the dash???
The black hose comes through the computer wiring grommet (think I already said that) and runs under the RH side of the dash until it connects to the hose harness going to the mode selector. It should be easy to spot. All you have to do is look for it.
Old Jul 4, 2009 | 04:00 PM
  #30  
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Originally Posted by shoebox
The black hose comes through the computer wiring grommet (think I already said that) and runs under the RH side of the dash until it connects to the hose harness going to the mode selector. It should be easy to spot. All you have to do is look for it.
it doesnt go through the firewall where the wiring harness does, it goes through on the top of the black A/C box, this is why I can't find where it goes because I can't find the hose under the dash, where it comes through is at the top of the firewall way up under the dash. Anyway where is the mode selector under the dash, maybe if I look there I will be able to find the hose and reconnect it. Thanks for the help Shoebox, Your website has really helped huge with this project.

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