supercharger 1999 gtp

[gp1985]

I recently bought a 1999 Grand Prix GTP which currently has about 127500 miles on it and I recently had changed the oil less than 150 miles ago with castrol syntec and a k&n oil and air filter. I haven`t noticed until that something was wrong with the supercharger, I was trying to beat a porsche cayman at the light and the boost gauge didnt move at all and there was a lack of a supercharger whine, but i let go of the gas then pushed it again at about 35 and the supercharger springs to life and i leave the porshe in the dust. Even now the supercharger works horribly(not working when accelerating from 0 but working fine when barely touching the gas and already around 40 or something)and the gas mileage has been absolutely horrible as well. I was guessing it had to do with the belt, coupler, or bearings exactly which i dont know. The guy at Canadian tire said the belt looked new, the car included complete service records and it says the belt was changed back at 80000ish. While searching on the internet i found a forum about changing the coupler on the unit but i don`t want to spend any money on that unless i know it for sure also there were no records of oil service done on the supercharger itself. Can someone please point me in the right direction.

[tblake]

Alright, so when you mash the gas, the supercharger boost guage shows nothing, but when you barly push it, it boosts a little? I guess Im confused a little.

[BNaylor]

You need to check to make sure the boost control solenoid is working properly before condemning the supercharger. A bad coupler will cause some sort of noise such as rattling. Most noticeable at idle. If the coupler is the original it should be replaced with the revised ones that have been available for several years now.

Also, check the condition of the supercharger drive belt.

[gp1985]

Originally Posted by tblake

Alright, so when you mash the gas, the supercharger boost guage shows nothing, but when you barly push it, it boosts a little? I guess Im confused a little.

its on and off, today driving home from school i pushed it down quite a bit at this one stoplight and it worked fine. Its not when i barely push it its whenever im already going... like i can be goin 35, 45, 60 etc. and floor it and the supercharger works fine like full boost. like i said, its on and off, but most of the time accelerating from 0 reguardless of how hard i push. Something i forgot to add was that sometimes it jerks without the rpms even moving.

[gp1985]

Originally Posted by BNaylor

You need to check to make sure the boost control solenoid is working properly before condemning the supercharger. A bad coupler will cause some sort of noise such as rattling. Most noticeable at idle. If the coupler is the original it should be replaced with the revised ones that have been available for several years now.

Also, check the condition of the supercharger drive belt.

don't know where the solenoid is... as i said, the belt still looks good no cracks or anything.. and as for any rattling noaise there is none...http://youtube.com/watch?v=WuAn2P7TSww <== is similar to how it sounds like at idle except not as loud...