2.0L LSJ Performance Tech 205hp Supercharged SS tuner version. 200 lb-ft of torque.

do i have a vacuum leak

Old 05-23-2019, 11:56 AM
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do i have a vacuum leak

07 lsj, pulls around 28 lbs of vacuum at idle, under boost goes up to 11 or 12. no codes, no aftermarket intake, does have zzp hiflow cat on it and is not tuned.. i dont believe that would affect the vacuum on it tho. as always i appreciate any help you guys have. yes my throttle body is clean haha idk if the performance is really affected by it but its also been like this since i bought the car.
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Old 05-23-2019, 01:35 PM
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Originally Posted by bahoodle View Post
07 lsj, pulls around 28 lbs of vacuum at idle.

Damn do you live on the bottom of the ocean or something?


In all seriousness I'm not sure why you are asking us if we think you have a vacuum leak when you describe everything as running fine.
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Old 05-25-2019, 03:10 AM
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i mispoke in the original post, its at 20 lbs vacuum at idle and -28 while cruising off throttle in gear. ive owned it for a year and it has always had vacuum like that, and its consistent. hasnt gotten worse by any means its always sat at -28 while cruising off throttle since i bought it. so im unable to compare how it feels driving now as to how it should drive normally i guess, thats why i asked if i have a vacuum leak..... i dont like you implying im stupid but understand why you did it lol the car had half of the main wiring harness eaten by a rodent and was keyed, so i picked it up for 1000 bux. fixed the wiring and its been a good daily driver ever since. but i havent looked into this issue cuz i didn't think it was a issue.
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Old 05-25-2019, 07:08 AM
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Your units are incorrect, it's not 20lbs. Maybe 20inHg, but 28inHg seems high but then again I'm not at sea level. It should be a higher vacuum at deceleration in gear than at idle
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Old 05-27-2019, 09:32 AM
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1 atm= 29.9inHg. Your vacuum number while under dfco is just fine.
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Old 05-29-2019, 08:47 AM
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Originally Posted by bahoodle View Post
i mispoke in the original post, its at 20 lbs vacuum at idle and -28 while cruising off throttle in gear. ive owned it for a year and it has always had vacuum like that, and its consistent. hasnt gotten worse by any means its always sat at -28 while cruising off throttle since i bought it. so im unable to compare how it feels driving now as to how it should drive normally i guess, thats why i asked if i have a vacuum leak..... i dont like you implying im stupid but understand why you did it lol the car had half of the main wiring harness eaten by a rodent and was keyed, so i picked it up for 1000 bux. fixed the wiring and its been a good daily driver ever since. but i havent looked into this issue cuz i didn't think it was a issue.
I'm just joking around with you. I was referencing that the most "vacuum" possible is atmospheric pressure which should around 14.7 psi or 29.9 in-Hg. You should have the highest engine vacuum during deceleration when the engine is pumping hard on the back side of closed off throttle body. Then during idle you still have good vacuum but not as much as when decelerating. According to what you have told us there is nothing that would suggest you have a vacuum leak. Like I said, based on what you have told us so far, I'm not even sure what led you to believe there may be a vacuum leak in the first place.
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Old 05-29-2019, 10:09 AM
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thanks for the help guys. i only thought i might because my lnf only drops to 20hg. at any time any gear, so i wasnt sure if i had a issue with the lsj n just wanted to ask ppl who know about it haha
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