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2001 Supercharger questions

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Hello all,

I have a 101k mile 2001 Regal GS and a 92k mile 2001 Ultra.

The Regal was in storage for 1 1/2 years awaiting a trans rebuild which is now done. It doesn't seem like the supercharger is providing boost anymore. If I read the dash gauge, it will only go to about 0.5 lbs. at 5000 rpms. But mainly it always stays at 0.0 under most acceleration.

I drove my wife's Ultra about 1 month ago and it seemed fine. Drove it today and now it feels like there is no boost at all. No dash gauge to read.

Can anyone tell me in a nut shell how the SC works on these cars?

Is there anything simple to check?

Any common issues with these?

Some kind of bad sensor that turns it off?

Is there a electrical clutch switch that engages the pulley?

Can something be unplugged?

Blown fuse?


Both cars run fine otherwise.



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The supercharger ought to be turning all the time the engine is running. At lower engine RPM you generally would not notice it because of the lower compression ratio and at higher speeds excess boost pressure ought to be routed out via the "wastegate". While the pulley is turning though there is a coupler between the pulley and the turbines of the supercharger. While this can get sloppy and make noise, I don't believe it is usual for them to break and stop the turbines from spinning.

I think you have a related, but two separate issues here. On the Regal I'd go over the vacuum lines and make sure they are all routed corectly. Perhaps they were incorrectly installed during the rebuild job. On the Ultra I'd check the vacuum lines for deterioration. The extra hood insulation does a good job cooking the lines. On the Regal I'd also consider putting a new Modulator valve on the trans. Even if it was replaced during the rebuild, it sounds like the trans is not shifting correctly.

On both I'd try to make sure that wastegate is opering right. When I put new intake manifold gaskets on my 95 Riv I noticed the turbines and the whole general interior of the supercharger chamber was coated with a sticky residue. I believe it was caused by the EGR valve dumping into the area just behind the throttle body and before the supercharger. I'm not certain the Series II engine routes the EGR that way, but if so, then the waste gates may be sticking open causing lack of pressure buildup in the superchargers.

Good luck

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The supercharger will built boost with rpm, but the wastegate keeps it controlled somewhat. We had a salesman who pulled a Regal GS for a demo. I went out to drive it after work one day. I drove it about 5 miles and them made the trip back. As I got straightened out on the access road, I nailed it. The boost gauge went to about 7.5psi initially, really quick, then as the rpm rose above 3000rpm, it eased back to the 5.5psi spec and stayed there to redline.

I believe the wastegate is run by a vacuum actuator, with the default mode being "open". Might just be a deteriorated vacuum line. Might also be a grounded-out knock sensor wire, which kills the ignition advance. Another side issue related to the knock sensor is flaky gas, or deteriorated gas.

Also, on the Grand Prixs with the SC3800, they have a boost gauge as a function of the Driver Info Center, but you have to pull it up via the menu to know it's there. I doubt the PA Ultra will have that, though.

Just some thoughts,


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