Possible vacuum leak or something else? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

oXeNo · 03-04-2012, 07:18 PM

Well I think I might have a vacuum leak? My car won't idle sometimes, sometimes it will, but its never at the same place sometimes it will sit at 2k sometimes at 1k. But it drives fine but when you get into boost, switch gears and keep trying to go, the boost drops and it slowly builds back up and it sounds like the turbo is spooled up still but I'm not sure but you can tell there is no boost there and the boost gauge slowly rises back up to about 12psi if I let it but it usually takes to long. If i can get it to idle and listen under my hood I can hear a hissing sound that makes me think its a vacuum leak, and from what I can tell it is from the intake side, It's an sr20det, hks ssqv bov, tial 38mm waste gate, manual boost controller, and a precision top mount turbo. Also, if I reach full boost in one gear let off the gas slowly and go back into boost, it wont build all the way it'll just go up to maybe 10 or so. I just went and checked everything I can't find any leaks in the intercooler piping I unbolted the c clamps and then bolted them back on and same thing, i also checked the vacuum tube that comes off the cold pipe into the intake.

Pro ViZIon · 03-04-2012, 10:38 PM

Check all your vacuum lines. Spray carb cleaner around all the hoses while the engine is running and check for a spike in the idle.

oXeNo · 03-04-2012, 11:07 PM

I will try tomorrow, it'll be hard to listen for one because the car never has a steady idle, it's always jumpy and won't sit in one spot for long. I am trying to figure out if the MAF could have something to do with this as well.

colombianbryan · 03-04-2012, 11:25 PM

try to go under your hood while the car is on and hear for any leak. also check your bov! it is pretty common for hks ssqv to have a vacuum leak. happened with mine and a friends!

oXeNo · 03-04-2012, 11:49 PM

I went under there and listened, I can hear a hissing that almost sounds like a vacuum leak. But I am not sure where exactly, The bov works i can feel it release pressure when I rev the engine up, but I am not sure exactly where the hissing sound is coming from. This is just one big pain, because from what I can hear I have compressor surge, which means all the pressure isn't coming out of the piping, which leads to the bov, I am not sure if it is because it isn't getting a good enough vacuum to open all the way or what. My boost gauge works correctly and it just kinda sits at -20 when the car gets down to about 1k and starts dying because it won't idle the gauge goes to about -10 then to 0 when there is no vacuum. This is my first Nissan I've ever owned, Ive only had hondas before, so far I love it. It's just this damn problem that is killing me, because on the way home driving it when I picked up the car it was running fine boost was at the full 15psi it was suppose to be, now I'm lucky if it'll sit at 12psi and when I switch gears it won't even go up back to that maybe 10psi. So I have no idea what to really look for, I've checked MAF, IACV, TPS, checked for exhaust leaks around the turbo manifold, fixed one and that helped, checked all the piping as well for leaks and nothing. I have felt around the BOV when at idle and didn't feel any vacuum leaks so it's just a huge hassle right now.

oXeNo · 03-05-2012, 08:53 PM

Ok so I have been messing with the car all day, I am starting to think it is just the MAF. On my wideband when it gets below 2k and tries to idle, it goes full lean, i have to pump the gas pedal a few times to get it to go back up, would the MAF cause my vacuum to be like this and not let it idle?

ShadowMan · 03-31-2012, 11:07 PM

like stated before, get a can of carb cleaner and spray around your vacuum lines one at a time and your ic piping as well, that will either help you isolate your leak or completely eleminate it as a possibilty of being your problem. You need to be methodical when diagnosing the problem so you can rule out what its not for sure instead just guessing and then having to go back to do it right.

ghettohatch · 03-31-2012, 11:57 PM

since you do already have a boost gauge hooked up check to see if the low vacuum occurs before the drop in idle, low vacuum at idle is a good indicator of a vacuum leak which will also cause that lean idle. and like stated earlier spray carb cleaner or something similar and check for a change or response which indicates it is starving for fuel. then repost.

also does the temperature change any of the symptoms? is it worse when cold?

03-04-2012, 07:18 PM	#1
oXeNo Zilvia Member Join Date: Feb 2012 Location: Thomasville Posts: 188 Trader Rating: (5) Feedback Score: 5 reviews	Possible vacuum leak or something else? Well I think I might have a vacuum leak? My car won't idle sometimes, sometimes it will, but its never at the same place sometimes it will sit at 2k sometimes at 1k. But it drives fine but when you get into boost, switch gears and keep trying to go, the boost drops and it slowly builds back up and it sounds like the turbo is spooled up still but I'm not sure but you can tell there is no boost there and the boost gauge slowly rises back up to about 12psi if I let it but it usually takes to long. If i can get it to idle and listen under my hood I can hear a hissing sound that makes me think its a vacuum leak, and from what I can tell it is from the intake side, It's an sr20det, hks ssqv bov, tial 38mm waste gate, manual boost controller, and a precision top mount turbo. Also, if I reach full boost in one gear let off the gas slowly and go back into boost, it wont build all the way it'll just go up to maybe 10 or so. I just went and checked everything I can't find any leaks in the intercooler piping I unbolted the c clamps and then bolted them back on and same thing, i also checked the vacuum tube that comes off the cold pipe into the intake. Last edited by oXeNo; 03-04-2012 at 09:05 PM..

03-04-2012, 10:38 PM	#2
Pro ViZIon Zilvia Junkie Join Date: Dec 2008 Location: Las Vegas, NV Age: 34 Posts: 415 Trader Rating: (0) Feedback Score: 0 reviews	Check all your vacuum lines. Spray carb cleaner around all the hoses while the engine is running and check for a spike in the idle. __________________ 1990 Nissan 240SX w/KA24DE - New project 1984 Mazda RX-7 GSL-SE 13B

03-04-2012, 11:25 PM	#4
colombianbryan Zilvia Junkie Join Date: Sep 2010 Location: Atlanta, GA Age: 33 Posts: 430 Trader Rating: (8) Feedback Score: 8 reviews	try to go under your hood while the car is on and hear for any leak. also check your bov! it is pretty common for hks ssqv to have a vacuum leak. happened with mine and a friends! __________________ I love drifting into curbs and guardrails

03-31-2012, 11:07 PM	#7
ShadowMan Zilvia Junkie Join Date: Jul 2011 Location: oceanside, CA. Posts: 538 Trader Rating: (4) Feedback Score: 4 reviews	like stated before, get a can of carb cleaner and spray around your vacuum lines one at a time and your ic piping as well, that will either help you isolate your leak or completely eleminate it as a possibilty of being your problem. You need to be methodical when diagnosing the problem so you can rule out what its not for sure instead just guessing and then having to go back to do it right. __________________ in any situation....thou shalt blaze

03-04-2012, 11:07 PM	#3
oXeNo Zilvia Member Join Date: Feb 2012 Location: Thomasville Posts: 188 Trader Rating: (5) Feedback Score: 5 reviews	I will try tomorrow, it'll be hard to listen for one because the car never has a steady idle, it's always jumpy and won't sit in one spot for long. I am trying to figure out if the MAF could have something to do with this as well.

03-04-2012, 11:49 PM	#5
oXeNo Zilvia Member Join Date: Feb 2012 Location: Thomasville Posts: 188 Trader Rating: (5) Feedback Score: 5 reviews	I went under there and listened, I can hear a hissing that almost sounds like a vacuum leak. But I am not sure where exactly, The bov works i can feel it release pressure when I rev the engine up, but I am not sure exactly where the hissing sound is coming from. This is just one big pain, because from what I can hear I have compressor surge, which means all the pressure isn't coming out of the piping, which leads to the bov, I am not sure if it is because it isn't getting a good enough vacuum to open all the way or what. My boost gauge works correctly and it just kinda sits at -20 when the car gets down to about 1k and starts dying because it won't idle the gauge goes to about -10 then to 0 when there is no vacuum. This is my first Nissan I've ever owned, Ive only had hondas before, so far I love it. It's just this damn problem that is killing me, because on the way home driving it when I picked up the car it was running fine boost was at the full 15psi it was suppose to be, now I'm lucky if it'll sit at 12psi and when I switch gears it won't even go up back to that maybe 10psi. So I have no idea what to really look for, I've checked MAF, IACV, TPS, checked for exhaust leaks around the turbo manifold, fixed one and that helped, checked all the piping as well for leaks and nothing. I have felt around the BOV when at idle and didn't feel any vacuum leaks so it's just a huge hassle right now.

03-05-2012, 08:53 PM	#6
oXeNo Zilvia Member Join Date: Feb 2012 Location: Thomasville Posts: 188 Trader Rating: (5) Feedback Score: 5 reviews	Ok so I have been messing with the car all day, I am starting to think it is just the MAF. On my wideband when it gets below 2k and tries to idle, it goes full lean, i have to pump the gas pedal a few times to get it to go back up, would the MAF cause my vacuum to be like this and not let it idle?

03-31-2012, 11:57 PM	#8
ghettohatch Zilvia Member Join Date: Nov 2007 Location: redlands Age: 37 Posts: 169 Trader Rating: (7) Feedback Score: 7 reviews	since you do already have a boost gauge hooked up check to see if the low vacuum occurs before the drop in idle, low vacuum at idle is a good indicator of a vacuum leak which will also cause that lean idle. and like stated earlier spray carb cleaner or something similar and check for a change or response which indicates it is starving for fuel. then repost. also does the temperature change any of the symptoms? is it worse when cold?