Bad pcv , can it cause a lost in boost pressure

Islandcat

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Like the title says. My car should be making 18 pounds of boost and it's at about 12. I changed the belt but that didn't help. I noticed that the connection on the pcv looks like it's leaking oil. I talked to my tuner and after reviewing my datalogs, he said I have a vacuum leak. I am gonna start with the pcv. Could that cause that large of a drop in boost, or it might be leaking somewhere else?
 

2011 gtcs

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Are you measuring boost with a aftermarket boost gauge or your factory gauge?
 

2011 gtcs

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No way it will show how much true boost the car is making without a MAP sensor or boost gauge of some sort. Are cars only have a MAF sensors so the ECU guesstimates on how much boost the car is making by how much CFM the MAF is reading, it's not way off but not accurate. Get a true boost gauge in there so you how much you're making. I'm not saying you don't have a boost leak or belt slip, but diagnosis the car properly so you're not chasing a problem that's not there. Who is your tuner?
 

Islandcat

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No way it will show how much true boost the car is making without a MAP sensor or boost gauge of some sort. Are cars only have a MAF sensors so the ECU guesstimates on how much boost the car is making by how much CFM the MAF is reading, it's not way off but not accurate. Get a true boost gauge in there so you how much you're making. I'm not saying you don't have a boost leak or belt slip, but diagnosis the car properly so you're not chasing a problem that's not there. Who is your tuner?

JMS. He is the one who told me I have a vacuum leak after reading the logs.
 

Islandcat

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and just a lil background. I never noticed a performance difference until I changed my rear tires to 305/45 nto5r. I thought the bigger tire killed my acceleration. Well I went to the track and only trapped 120. With my mods I thought I should be closer to 130 or so. Well I messaged black99lightnin on here and talked to him cause I remember him struggling at the track cause of a larger tire one time. He told me no it wasn't that big of a difference, check my belt to see if its slipping. Well I didn't notice much dust on my pulley, so I went datalog my car to send to my tuner. That is when I noticed my guage reading 12 pounds. It used to peg it out easy. Anyway, I got the belt changed at dealership along with them checking boost blow off valve (good), and it still didn't change anything, so I talked to my tuner again and he reviewed the datalog, and said it was adding fuel at cruise and wide open. He said that means I have a vacuum leak. So I got the Dealership to order new PCV valve, and we gonna replace that next week ( they also said one of my radiator hoses was leaking and will be replaced next week too). He also said he got a smoke machine and will check everywhere for vacuum leaks. I was just mainly wondering if a faulty PVC could cause that, so I can put my mind at ease a lil bit. My mods are below for anyone that is curious.

13-14 TVS with 2.4 pulley
67mm VMP throttle body
123mm CAI
off road h-pipe
3:73 gears,

I think that is all.
 

2011 gtcs

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Have you looked into a gates blue belt for belt slipping issues? I haven't heard of our PCV valves having a lot of issues. But it's always a possibility the PCV valves just twist out and can easily be replaced. Do you have aftermarket catch cans.
 

Islandcat

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Have you looked into a gates blue belt for belt slipping issues? I haven't heard of our PCV valves having a lot of issues. But it's always a possibility the PCV valves just twist out and can easily be replaced. Do you have aftermarket catch cans.

yes sir, I have a bobs catch can on it. I changed the belt and put a ford one on. I don't believe there is any belt slip at all.
 

black99lightnin

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that was my first thought actually. I still run that lil fitting that you made for it lol. I am gonna make them check everything with their smoke machine

Good luck. If they can't figure it out and you want to run it to Paulina(Lutcher/Grammercy area), I'll be happy to look at it with you on Sunday.
 

2011 gtcs

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yes sir, I have a bobs catch can on it. I changed the belt and put a ford one on. I don't believe there is any belt slip at all.

Just for fun. Did you start noticing a change after you put the catch can on? maybe put the stock PVC hose back on and see how the car runs.
 

Snoopy49

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Just for fun. Did you start noticing a change after you put the catch can on? maybe put the stock PVC hose back on and see how the car runs.

If you didn't get the drain valve fully closed, you will get a vacuum leak. Sometimes the bottom of Bob's separator isn't fully tightened and that may be a cause of leakage. I wasn't able to tighten mine because the nipples on the can wouldn't line up for the hoses. That was 5000 miles ago I haven't had a problem.
Another potential problem with the Bob's separator is that it is possible for some of the filter material to get caught in the drain valve, keeping it from fully closing. I had this happen on mine and got an extra screen for the bottom of the can. This keeps the filter material out of the valve.
 

STACKZ89

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No way it will show how much true boost the car is making without a MAP sensor or boost gauge of some sort. Are cars only have a MAF sensors so the ECU guesstimates on how much boost the car is making by how much CFM the MAF is reading, it's not way off but not accurate. Get a true boost gauge in there so you how much you're making. I'm not saying you don't have a boost leak or belt slip, but diagnosis the car properly so you're not chasing a problem that's not there. Who is your tuner?

I have to agree here... I just installed a auto meter boost gauge (mechanical) and I can say that it reads 2-3 lbs higher then the factory gauge...
 

Islandcat

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Thanks for the offer blacklightnin, but I am bringing it to dealership Tuesday to fix radiator hose and pcv. They gonna hook up smoke machine to it.

I been having the catch can. This performance difference wasn't noticed until well after I put it on. But I ain't never drained it since I got it. It might be full lol.

I may play with the catch can tomorrow to see if it is messing up.
 

Troponin

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No way it will show how much true boost the car is making without a MAP sensor or boost gauge of some sort. Are cars only have a MAF sensors so the ECU guesstimates on how much boost the car is making by how much CFM the MAF is reading, it's not way off but not accurate. Get a true boost gauge in there so you how much you're making. I'm not saying you don't have a boost leak or belt slip, but diagnosis the car properly so you're not chasing a problem that's not there. Who is your tuner?
Most tuners can use the air load as a way of determining a boost leak or belt slip. All you need is a baseline, and in most cases, they have tuned enough cars with the same application to have several. MPT did exactly that for my truck and found belt slip without knowing what the actual boost was.
 

Islandcat

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Brought it yesterday. Changed pcv valve, and did the smoke test after. All was good. Got in it and my supercharger made that high pitched wine like it used to. I don't think my boost was down 6 lbs( probably the gauge was reading wrong), but now it definitely sounds like it was where it was supposed to be. It definitely felt more powerful, especially between 2,000 to 3000 rpm. Datalogged it this morning, and sent it off. Something still ain't right. They told me to check intercooler pump to make sure it's working(it is working),but they really thinking I have a bad o2 sensor. They said my two banks are off pretty bad, and my car is only giving 10-12 degrees of timing( I am not sure what it should be, but I guess it should be higher obviously). Anyway I ordered 2 new o2 sensors(they only 60 a piece) and will change them next week. Then will data log and try again lol.
 

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