Ugh.... No Boost.... AGAIN!!!!! - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Forced Induction All questions and problems regarding Superchargers, Turbos, NOS, ZEX, intercoolers, water injection, etc.

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Old 08-11-2004, 08:34 PM   #11
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DrJay,

Where would I be listening for a leak.... and when?
Would I be able to hear it when the engine is running and she'* idling.

Also, where would I put this foil? the stopper nut?
Sorry, I'm kinda dumb under the hood... can you explain it a bit more.
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Old 08-11-2004, 08:54 PM   #12
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Hey nada problem....

If you start the car and hang your head under the hood you should hear a loudish "SSSSSHHHHHHHHHH" which would indicate a leak. Be careful to distinguish what your intake sounds like so you don't confuse the two. A vacuum leak will be more high pitched than your intake so stick your head up to your filter to get a reference. Sometimes it can be hard to find because its like a police siren, you can hardly tell where its comming from! The best way I've found is to put your head behind the intake so you can't hear it as much.

I'm assuming you know what the boost control solenoid is since this will be your second time replacing it. If not let me know and I'll post a picture. If you look at your BCS you'll see a shaft that comes out the bottom and attaches to another shaft that goes into the supercharger. With your engine off the shaft from the BCS will be resting on a small screw head looking thing on the supercharger. When you start your car the vacuum will pull the BCS shaft into the BCS itself and lift it off that screw head looking thing. I'll call the screw head looking thing the stopper nut from now on. When you floor it the BCS pushes the shaft out until it hits the stopper nut, this closes a valve in the supercharger and allows full boost. When you let off the gas it pulls it back up, bypassing the supercharger and taking the boost back away. What we want to make sure of is that the valve in the supercharger is being closed all the way. i.e. the BCS is pushing the shaft all the way out until it hits the stopper nut.

Take a piece of tin foil and with the car running (so the BCS shaft isn't sitting on the stopper nut) affix a piece of foil to the stopper nut allowing a piece of it to stick up. Make sure this piece sticking up is plenty more than thick enough to hold up its own weight. Note how long and in what position this piece sticking up is. Take it for a short drive and floor it only once. Then pull over ASAP and check the foil. If its working properly it should have crushed the foil all the way to the stopper nut. If not you should be able to tell how far it did make it. The idea might take a bit of refining but it should work.

Backing up some....obviously you want to make sure the BCS shaft is resting on the stopper nut before bothing with all this

Lemme know if you have any other q'*
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Old 08-11-2004, 10:18 PM   #13
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Quote:
Originally Posted by DrJay
If you look at your BCS you'll see a shaft that comes out the bottom and attaches to another shaft that goes into the supercharger. With your engine off the shaft from the BCS will be resting on a small screw head looking thing on the supercharger. When you start your car the vacuum will pull the BCS shaft into the BCS itself and lift it off that screw head looking thing. I'll call the screw head looking thing the stopper nut from now on. When you floor it the BCS pushes the shaft out until it hits the stopper nut, this closes a valve in the supercharger and allows full boost. When you let off the gas it pulls it back up, bypassing the supercharger and taking the boost back away. What we want to make sure of is that the valve in the supercharger is being closed all the way. i.e. the BCS is pushing the shaft all the way out until it hits the stopper nut.
Ok... you said at rest the BCS should be resting on the "stopper nut"... it isn't.
It rests about an inch above it. When I start the engine I can see it get 'sucked' into the black cylinder thing.

I tried with the foil, and as far as I can tell, it only goes down as far as it does when the car is off. I'm not 100% on that... but I've fairly sure.

I tried moving the lever, it will go up easily, but it won't go down very much, maybe 1/8th of an inch.

EDIT: I couldn't hear any vacuum leaks....
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Old 08-11-2004, 10:31 PM   #14
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Play-doh. It works great for checking clearances and gaps.
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Old 08-12-2004, 12:10 PM   #15
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Ok Dr.Jay.... I did the bypass trick.

I don't think the bypass trick really helped, but what I did was try and move around that lever... using a screw driver I was able to push it down until it hit the "stopper screw".
I moved the lever up and down a few times and it seems to move a bit easier.

I took the car for a test drive and now I'm getting inconsistant boost.
Sometimes it'll only go upto 1/3rd on the plus side... other times it goes to almost 3/4 of the way. It'* still not boosting like it should (I used to burry the needle everytime at WOT).

The bypass valve is still kinda sticky... and when the car shuts off it doesn't rest of the stopper screw, but it rests closer now. I'd say 1/2 inch, compared to the 1inch.
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Old 08-12-2004, 10:51 PM   #16
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UPDATE

After talking on MSM w/ Dr.Jay about my problem,
I completely removed the BCS and the BCV.
I determined that the "sticky-ness" was from the lever coming out of the SC and not the BCV.
I re-attached the BCV (in bypass form) and BCS. When I reconnected the BCS I noticed that a vacuum line between it and the SC was cracked at both ends, not by much at all, but just enough to make it kinda loose compared to the others.

I went to my mechanic and got a new hose and tried it.....
I am now easily getting 1/2 boost most of the time, and FULL BOOST some of the time.
I've noticed sometimes the needle goes to 1/2.... and then kinda trys to 'push' higher but fails..... sometimes it 'pushes' a bit and then FLYS upto full. Other times it just gradually goes to full.

I've got a new BCS and BCV on order, they should be in next week. I'll be trying both to see if they make a difference.
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Old 08-13-2004, 12:06 AM   #17
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Vacuum leaks will suck in debris. Making internal parts on the BCS and BC actuator gummy and sticky.

Sounds like your'e on the right track.

I TOLD you it was probably a vacuum leak
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Old 08-15-2004, 08:51 PM   #18
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Quote:
Originally Posted by willwren

I TOLD you it was probably a vacuum leak
yea yea yea.... you're soooo smart...
but seriously thanks for all the help... everyone

I've been driving now for the past few days and she seems to be 99% better.
Bit of a needle wobble while idling, but nothing big.

Anyways thanks again all.

PS-Shoud I clear the P0441 code from the computer and see if it comes back?
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Old 08-15-2004, 08:53 PM   #19
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Quote:
Originally Posted by Merlin 91/97
PS-Shoud I clear the P0441 code from the computer and see if it comes back?
Yes, clear the code and start fresh.
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Old 09-05-2004, 03:14 AM   #20
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How did you do the scan of your codes? How could I find if there was a code off in my car?
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