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

How to find a BAD vacuum leak?

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Old Jul 16, 2006 | 07:54 PM
  #16  
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Re: How to find a BAD vacuum leak?

Originally Posted by Sweetred95ta
I would say adjust the throttle body blades open some and see if you can't get it at a high idle. If you could do this, you could test using the starting fluid method. If not, then loosen all of the valves and use racerdude1's method, which is very clever btw.



Thanks
Old Jul 17, 2006 | 06:59 PM
  #17  
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Re: How to find a BAD vacuum leak?

Originally Posted by Sweetred95ta
I used duct tape and it worked fine. Just make sure it is pinched or folded over and it will seal.
Lol, I was actually just kidding about using duct tape, pretty sweet that it'll actually work. I'm gonna go try this in a bit.

Originally Posted by sweetred95ta
You shouldn't have to worry about the car running too lean at idle, because in the tuning tables, with that high of a MAP at idle, the car should run rich. Basically, it thinks there is a load on the car at idle and SHOULD feed it more fuel.
Yeah.. that was actually the problem for the longest time, the map is so high that it would just dump fuel in at 10-15% duty cycle on the injectors where it would run so rich that it would completely fumigate my garage and go into my house and let 3 quarts of fuel past the rings and into the oil pan all in about 2 minutes of run time.

Now, with the retune leaning it out 60% AND using the stock 22 lb/hr injectors it runs a tad lean around idle if I keep open and closing the thottle to allow it to run, but if I hold the throttle open it lets too much air in and doesn't add enough fuel and it just dies out.. So pretty much if the leak is at a hose, it should be so lean that it shouldn't even run.

Originally Posted by sweetred95ta
I would say adjust the throttle body blades open some and see if you can't get it at a high idle. If you could do this, you could test using the starting fluid method. If not, then loosen all of the valves and use racerdude1's method, which is very clever btw.
Cool, if this taping off the manifold nipples doesn't give me some more vacuum, i'll try and throw the 42 lb/hr injectors in (that should put right back at running richer than hell) and see if it will high idle with the throttle stop screw out all the way (1.18V). Thanks for the help.
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