Hi all, I'm extremely new to this forum but I didnt have nowhere else to go for help. I have a 1997 grand prix gtp with a 3.5" pulley and a cold air intake. I can't drive the car now because it makes an absolutely awful noise that sounds like it's coming from the intake but it's not the supercharger I just replaced it. This noise had happen before I replaced the gaskets underneath the supercharger and I still did it, I replaced some vacuum lines and it stopped! After about 2 and a half weeks it started again. I replaced the supercharger thinking that was the problem but it is STILL making that noise and idling high (around 3000rpm) and I have no idea what it could be. I asked a local mechanic he said sounds like a bad vacuum leak but I have no idea where to start plz help!!

welcome to the site. I'm not one of those guys that's blown, but have you checked the blow-off valve? Iirc, yall still have the same vacuum modulator on the firewall side of the engine as us N/A guys, have you bothered to make sure that modulator is still good? lessee...what else is vacuum related up top around there...EGR? MAF? MAP? There's a few lines up there, chase em down and inspect closely for tears, rips, holes, breaks...ya know...good luck.

Hey, guys, there's a vacuum modulated idle speed controller, isn't there? iirc, my 00 has electronic idle speed control.

Thanks for the suggestion I'll have to check em out closer and when I swapped s/c's I swapped blow off valves to so I'm not sure that it would be the problem. I had replaced all the vacuum lines but I'll check em again it's just drivin me insane, the cars been down for months...

It seems more of the blown guys are online right now, so you might be able to get a better idea of what to look for. Sorry I can't REALLY point you in the right direction.

Take lots of pictures of all the vacuum lines around your supercharger including the top and around the bypass valve (its not a blowoff valve just so you know) and also around the throttle body. Also take pictures of where they go. We'll get it figured out.

Can you hear where the noise is coming from?

Just curious. If you pull your dipstick out when its running and making the noise does it go away?

Ok I'll try and get some pictures off all of the vacuum lines tomorrow and no I haven't tried that, never even thought of that really I could take a video as well and post it to YouTube so you can actually hear the sound it's making maybe that would help.

Sure. It will all help.

Probably not your problem maybe your s/c coupler could be bad in both snouts you have?

http://www3.sympatico.ca/aepa/blowerinstall.html

Wouldn't cause high idle. Neither would PCV like I was originally thinking was the noise.

When you replaced the s/c, what year did you replace it with? The 97's have an extra vacuum tree coming off the front of them near the bypass valve.

The one that I put on it was off a 99 it doesn't have the vacuum tree and I'm not sure how that would affect it but I kno it's not the s/c cause this one is really quiet and I kno it was good. My friend just had it rebuilt then his oil pump went out so I don't think that's the problem. But I'm going to take a video of it here in about 10 minutes and get some pictures of the vacuum lines to

Ok here the link to the video let me kno what u think http://www.youtube.com/watch?v=HK6qmbquyzM&feature=youtube_gdata_player

I would start by redoing some of the vacuum lines; the one going into the side of the throttle body doesn't look quite right to me. There should be a vacuum "T" and a tube to supply vacuum for the modulator valve on the trans. See view A on the bottom right of this pic:



Image and part#s courtesy of www.compnine.com

The GM part numbers for 16 and 17 in that pic are:

16: 24506302 PIPE,A/TRNS VAC MOD(ACDelco #24506302)
17: 24502852 CONNECTOR,A/TRNS VAC MOD PIPE(3-WAY TEE)

Hope that helps!

Ok thanks I'll have to check it out! Do you kno where that valve on the tranny might be? My book don't tell me none of that..

Here's a pic of the 4T60E trans with the valve installed (note the vacuum line):


The factory valve is slightly bigger:



If it doesn't have the modulator valve, then you have the 4T65E trans, which has shift solenoids inside the trans. '97 was an odd year for these cars..

Ok when I get time tomorrow il check it out and see if it had it thnx for all the help so far guys