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

how to check vacuum?

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Old 01-15-2005, 05:33 PM
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how to check vacuum?

I'm still troubleshooting my car, stumble/missing.

http://web.camaross.com/forums/showthread.php?t=329594

I checked the fuel pressure, I'm good at 43 key on engine off and 38 engine on idling, holds well. I also checked the resistance of each injector, they are all within spec.

I also disconnected my knock sensor and replaced my lt4 KM with an LT1 KM and reset my computer. Most of the time I'm getting 0 retard but it still retards the timing at times, at WOT though it runs like a raped ape most of the time. It seems that most of the stumbling/missing comes at part throttle and ESPECIALLY when i'm in a high gear and load the engine it bucks. Also at idle it seems to miss a little bit/idles rough. But it seems to run better with the less knock retard it pulls, but there is still something else because it still isn't 100% at idle.

Now I want to check vacuum, so I bought a guage/pump and need to know where to put the hose exactly, i'm not sure. I tried to take out the opti vent tube from the intake elbow and put the guage there, it just read 0. Where am I supposed to read for vacuum???

Last edited by Hawk; 01-15-2005 at 05:36 PM.
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Old 01-15-2005, 06:17 PM
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Re: how to check vacuum?

The hose to the elbow is a vent-not vacuum. Pick one of the small ports on the side of the intake. You can also monitor vacuum through the MAP sensor via diagnostic software or a scanner.
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Old 01-15-2005, 06:23 PM
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Re: how to check vacuum?

didnt really read the post, but get a boost (or just vacuum) gauge, and plug it into one of those things sticking out of the intake on the side
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Old 01-15-2005, 06:37 PM
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Re: how to check vacuum?

cool thanks, i'll give it a shot


Brian
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Old 01-16-2005, 10:40 AM
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Re: how to check vacuum?

Or if you have one of the gauges with larger ports you might have to undo the vacuum brake line from the elbow on the master cylinder and stuff her in the line.
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