FAQ: Boost Bypass Valve/Boost Control Solenoid Questions (No Boost)

deekster_caddy wrote:

Knock is erratic because you have full boost all the time. I wouldn't run like that besides the test.

Morad's probably has plenty of BBVs.

i understand sir, i actually have everything plugged back in so im back to max boost of 3 pounds or so haha... but i would prefer a new valve, not only because i know it will last till the car is done with, but because i get parts for cost

LT1Squirrel wrote:

i would prefer a new valve, not only because i know it will last till the car is done with, but because i get parts for cost

No problem at all. Just making sure you fully understood what was going on. I prefer new parts when I can get them too but sometimes used is just too much of a bargain to pass up.

is 1997244 what i should be purchasing?

Based on the location and description, I think so. Don't shoot me if you get the wrong part though.

Hi,looking for information on the '95 Riv boost control solenoid/valve, or waste-gate solenoid valve. GM#12353309 has been discontinued. RockAuto does not show anything I could find under the '95 Riv. I have read this part, for a series 2 engine is not compatible with the '95. Is this true? Anyone with the '95 replaced this item, and what # would I try and find today?
Thank you! 
 

I replaced mine with a boost control solenoid from another 95 Buick Riviera at a local Junkyard. I believe that the series 2 solenoids will actually work on the 95. I think they are the same just mounted slightly differently, so make sure to keep your bracket. Check out this site to see how to test them and for more info.

http://www.3800supercharger.net/diagnosing.html

Is it typically the solenoid that goes bad or the mechanical actuator?

My actuator stopped sealing properly. If you push in the actuator manually and cover the vacuum ports with your fingers, it should stay compressed. My old one did not hold at all.

I have searched every forum that has 3800 s/c know how and can't find my problem.... the car is an 1987 fiero and the motor is out of a 1997 Riviera s/c. Everything is stock except kn filter.

I was driving to work winding through the gears with everything working normally. I hit a red light. I go to accelerate and it is lacking power. I try to hit boost and it stays in vacuum the entire time.

So far I have bypassed the bbv with no results. The plunger moves up and down. Vacuum on the car at idle is at 20. The only codes being thrown r trans codes for obvious reasons and o2 codes. I have also taken off the belt to see if the coupler is still attached and it is.

Any kind of input would be appreciated

Please explain exactly what you mean when you say 'bypassed the bbv' and 'trans codes for obvious reasons and o2 codes' - having no boost shouldn't throw any codes.

Some ppl were saying that the "boost bypass valve" (bbv) could have been my problem. So I took the bottom line off and put vacuum caps on both the solenoid and on the bbv itself.

Trans codes bc the original auto trans is gone and the fiero 5 speed is currently attached. So the codes are coming up because none of the sensors are reading.

Shoot a PM to Mr.Riviera. He knows a good bit about the superchargers and if anyone could help it would probably be him.

Pm'd thanks!!

Check map sensor and all vacuum connections.

Map will b checked tomorrow. All the vacuum lines looked prettu good to me

Check O2 sensor fuse.

I haven't checked any fuses because I figured it was all mechanical but I will check that today too

zip_tie wrote:

Some ppl were saying that the "boost bypass valve" (bbv) could have been my problem. So I took the bottom line off and put vacuum caps on both the solenoid and on the bbv itself.

Trans codes bc the original auto trans is gone and the fiero 5 speed is currently attached. So the codes are coming up because none of the sensors are reading.

When you capped off the bbv, was it in the fully down position?  IE, was there spring pressure where it kept wanting to push out?  Capping it off properly away from the solenoid and vac system should cause it to only be in extended position, which would be in "always boost" mode.  Regardless of anything else in the system (vac or MAP, or computer), if the BBV is in the down position you should have boost.  If the bbv doesn't default to pushing extended, then you have a ruptured diaphragm inside it and it needs replacing.  Even if its ruptured, you can test by wedging it in the downward position with a bit of wood.  Wedged down you SHOULD see boost.

Also, its a long thread, but things to try and troubleshooting can be found here:
https://rivperformance.editboard.com/t2083-faq-boost-bypass-valve-boost-control-solenoid-questions-no-boost

zip_tie wrote:

Some ppl were saying that the "boost bypass valve" (bbv) could have been my problem. So I took the bottom line off and put vacuum caps on both the solenoid and on the bbv itself.

Trans codes bc the original auto trans is gone and the fiero 5 speed is currently attached. So the codes are coming up because none of the sensors are reading.

Thanks. Sorry I missed the Fiero bit so trans codes make sense now. Completely irrelevant that it's from a Riv.

Take a vacuum tester and put suction on the BBV. Does it move when you put vacuum to it? Does it hold vacuum?

Well I have boost now. I cleaned the maf, found a few cracked vacuum lines and replaced the throttle body and upper intake gasket. Thanks for all the help. I'm not sure what worked but I did see coolant leaking from a gew spots and it has ceasef now

Now time to figure out race car parts

so my gauge reads that I am only running 4psi of boost, and ive viewed videos on these rivieras and im sure that my car can be a lot faster if im running the proper amount of boost. the only known problem I have is I have to replace my lower intake gaskets. which someone has told me it has nothing to do with boost. anyone else had this low of boost before? im 5k above sea level but I don't thing it would be that dramatic. I have also sprayed starter fluid all over to make sure I have no vacuum leaks, no sign of one.

I posted this awhile ago, but it moved threads, so you might not have seen it:

Me wrote:

Your boost gauge is hooked up wrong or you aren't making any boost.
"I hooked up the vacuum line and everything done right but it goes to negative 15psi and when I punch it, it goes to 0psi, so do I need to adjust the needle? And when the needle is off and car is off it goes to 0psi."

If working and hooked correctly you will see the neg(vac), but under load you will see positive boost.

Also post pics of your boost gauge install. Check for BBV movement under the hood when blipping the throttle. That’s the black actuator arm on the SC on the front right when facing you. If you reach over to the TB and give it a solid rev, you should see the actuator extend.

I suspect the not displaying boost and "vtec" thing are separate issues if you still see no boost under the "vtec" condition.

The takeaway here is you need to check a few easy things:
-First get your boost gauge sorted.  If it is indeed hooked up properly, then be sure the needle reads 0 when the car is off and in the negatives when running.  Or alternatively, get an aeroforce working correctly to display boost.  This takes you to step 2 in troubleshooting this.
-Check your boost bypass actuator.  Its the black piston plunger thing on the right near the intake when facing the engine.  What it does is throws a mechanical lever to close off the inlet of the supercharger with the inside of the LIM.  In a nutshell, extended all the way you make boost, retracted you bypass the air to the inlet to not make boost.  Verify that you can move it up and down freely.  It will have spring force in the extended position when the car is off.  When idling it should retract into the up position.  If its movement seems to be normal move to step 3.
-Check that the actuator extends fully when the engine is under load.  You can do this under the hood with the engine running by blipping the throttle.  The piston should extend and retract related to the brief load that revving puts the engine under.  After verifying that it can move itself move to step 4.
-If movement seems ok but boost is still low, you likely have a bad boost control solenoid.  The solenoid is the little rectangle thing with the wire and vac lines going into it.  Sometimes they can die or partly die.  The result is that it doesn't switch the vacuum source properly and the piston on the actuator won't extend fully under high engine load.  Result: only 2-4 psi when you expect 6ish stock.  If you think it may be the solenoid, you test by changing the vacuum routing so that the BBV piston is always extended and go for a drive.(Can't remember the exact changes to do this off the top of my head.  It’s on the forum somewhere, or perhaps someone else will jump in.)  If that was the culprit you will see full boost. Don't drive for long though, the car will idle like crap and not coast very well as the engine will be operating always under boost and not ever letting it bypass as needed.


Without seeing the car, and if everything else is correct, I'm going to bet your issue is related to either the solenoid being bad, wiring to it, vac routing from it, or issue with the BBV actuator itself. Theres not much else that can cause a low boost situation by a few PSI.

ok I was showing nearly zero awhile ago, ive replaced the boost bypass actuator and then reading about 4psi of boost sometimes even 5 if im lucky! so I think the problem is the bad boost control solenoid. im going to see if I can find any write ups. my car idles like crap, but I was thinking it was the intake gaskets doing that?

how do I test it? I cant seem to find the forum.

You can bypass the boost solonoid by hooking the top vac line on the actuator to your top vaccum t. https://2img.net/h/i1309.photobucket.com/albums/s639/fieroaddicted/fiero%20build/109_5673_zps9a6de273.jpg

Only try it temp to see if your boost goes to what is expected.  Be sure to cap off any lines removed to do this. Only do it like this for testing.