half boost... supercharger problem...power loss

hello again everyone. my super charger recently stopped making full boost according to my DIC, its only goin up half way at WOT and theres is a deffinate loss of power. does anyone know what this could be? i was told that the coupler on the supercharger will need to be replaced soon but he didnt mean this soon, is this the proble? thanks

Is the supercharger ratteling at idle?

I dont think a bad coupler will cause loss of that much boost.

well it used to rattle quite a bit, but once it stopped is when it stopped boosting all the way. another thing i noticed is that it no longer makes a wining sound like a supercharger should unless its revving around at least 4000

no one knows?...

I would assume the rattling coupler didn't just fix itself, so I would say it is related to the boost issue. It could also be a bad boost valve or catalytic converter issue, as excessive exhaust backpressure won't allow boost to build.

how can i narrow it down? is there anything i can test on my own

well can anyone please help me because this really needs to get taken care of before something else goes wrong because of it. are there any ways to help diagnose what the cause is

Are you getting any type of noises from the supercharger? Mainly any rattling? If so then the snout should be removed for a closer inspection of the coupler.

im pretty sure the coupler is going, if it hasnt already gone... but before i replace that i really need to know if thats the cause of the very low amount of power im getting. i dont wanna spend the money to replace it if the whole supercharger is messed up. it does rattle, it used to rattle more. im assuming its because its in such bad condition but i dont know for sure.

Well, take it apart. You'll be able to tell if the coupler is bad by elongated holes.

ok a few questions before i do tho. what do i need to take it apart and rebuild it? how long should it take? in the event i should need a new coupler will i be able to drive without it for a few days? where should i get a new one from?

there is a writeup in the tips and maintenace subforum. Basically remove the alternator, SC oil, and snout. Its not too hard. A coupler can be purchased from ZZP. Its not very expensive.

I would not recommend driveing around with your SC apart. In fact don't do it. I would just order the coupler and some SC oil from ZZP. Combined you are probably looking at less than 50 bucks, and if it doesnt fix your problem, you aren't out too much.

As dumb and obvious as this may sound, I once had a buick park ave with the 3.8l SC'd v6.

It had the exact same issues.

I swapped the Plugs / Wires. Cleaned the MAF, threw some injector cleaner in and it ran like a top.

Sometimes the most obvious thing may be the problem, it's easier to check / replace the small inexpensive things than jumping straight into cpu replacements.

Also check for vacuum leaks. You should be able to purchase a gizmo from the parts store to check for vacuum leaks, basically it hooks up to a dormant vacuum line and injects colored smoke, which expells through the leak.

Gentlemen this member has had ongoing issues with his GTP and even planned to get rid of it. I would recommend reviewing the following threads before providing advice to cut down on redundant replies and confusion. See below.


it was good while it lasted... (http://www.automotiveforums.com/vbulletin/showthread.php?t=925018)

check engine light. code P0171 (http://www.automotiveforums.com/vbulletin/showthread.php?t=921271)

ha ya ive already been over all that ha. thanks anyway but ya ill try a coupler then. while im in there id like to run a thicker wire from my alternator to my battery because of my audio system, is there anywhere to connect a 4 gauge wire on the alt.? a positive post or anthing? thanks

Gentlemen this member has had ongoing issues with his GTP and even planned to get rid of it. I would recommend reviewing the following threads before providing advice to cut down on redundant replies and confusion. See below.


it was good while it lasted... (http://www.automotiveforums.com/vbulletin/showthread.php?t=925018)

check engine light. code P0171 (http://www.automotiveforums.com/vbulletin/showthread.php?t=921271)Thanks! I'll take a look and see what all the combined problems are. I hate redundancy! Lol

i just read on zzp something about adusting they bypass valve... apparently if it does not close all the way, it may cause me to be unable to achieve full boost at WOT. this sounds exactly like my problem (aside from the coupler rattling). does this sound probable? and is it safe? here is the link http://www.zzperformance.com/grand_prix/articles1.php?id=56

It should be safe, however adjusting the bapass valve wont increase boost, it will only change how soon boost occurs. It will do nothing if your supercharger cannot put out any boost to begin with.

oo ok. well ill try it and see what happens because i do get boost, just not as much as i should. and if that doesnt fix it then i guess im gunna have to replace the coupler. should i get the bearing replacement kit as well? and how sure are you that a bad coupler would be the cause of the low boost pressure, like how probable is it that that is the cause

You mean the snout bearings and front seal? Won't hurt. The bearings will have to be pressed out and in so you will need automotive machine shop service. The other option is to replace the snout.

Be sure to check the boost solenoid electrically. Makes sure there is 12 volts at the connector which is from IGN 1 - UH circuits. The PCM module supplies the low when needed.

well i truly appreciate all of your help everyone, but as it turns out it was as simple as whoever last serviced my engine unplugged the boost bypass valve plug. i plugged it back in and everything seems to be working fine now. but just wondering, will adjusting the bypass valve allow any more power? again thanks for your help

What do you mean they unplugged it? The valve only has a vacuum line going to the top of it. Did they unplug the vacuum line?

Your still going to replace the coupler right?

if i was lookin at the right thing, theres a plug on the bottom of with 2 prongs in it, and it was unplugged. and as for the coupler, not right now, but i will soon.