2004 Buick Regal Super Charged - Rough Idling On Start-Up, Braking Weakened Afterwards

As I start up my vehicle on a 7:30 AM morning, the engine runs rough while idling from 2000 RPM to 3000 RPM. As I am driving it out of a parking lot, the same behavior occurs in DRIVE, and the steering wheel seized up for at least 10-15 seconds, then returned to normal. When the vehicle was stopped at the parking lot exit, there was light jerking in the entire car from the rough idling, as if the vehicle was trying to escape from the brakes. When I get the vehicle up to at least +20 MPH, everything runs smoothly as if nothing is wrong. But stopping causes the same rough idling result. The drive was at least 10 minutes. Then at 1:10 PM in 79°F weather, the same result occurs as I’m driving home but then I notice my brakes were becoming hard to decompress, as if the vehicle was off and I pumped the brakes. This resulted the brakes losing their own braking power! Making it very difficult to stop in intersections. I needed to brake much earlier than usual to get the vehicle to stop in time. The braking issue and the rough idling are constant events now, and the steering wheel seizing up from the morning was a one-time occurrence.

So what are you going to do when that 3 year old child steps out in front of your car ?

Get this car towed to a shop ASAP


As much as I appreciate your near-instant response, this doesn’t seem to help my issue. I need troubleshooting recommendations, not a website i’m looking answers from, telling me to go to a shop. The vehicle is parked safely.

Is the check engine light on ?
If yes, what are the codes ?

CEL is off.

Does it work, does it come on when the key is in the run position and engine not running ?

Yes. When the vehicle is in Retained Power Mode, CEL is working normally. All issues stated above sparked just this morning.

Turn all accessories off, including AC. Start it up, Good idle? No? Take a good look at all your pulleys and make sure they are running smoothly, especially the supercharger pulley. Has the supercharger ever been lubricated? There is a reservoir I believe for lube.

How many miles on this car? And engine? And supercharger?

I am asking these questions because I’d guess, given a lack of information you gave us about about the car, the supercharger is dragging down your idle and killing the vacuum for the brakes.

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Possibly a bad MAF or a vacuum leak.

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Hello Mustangman,
I apologize for any lack of information I have handed. I’m trying to hand out as much as I can think of given my situation.
When the A/C is activated, it increases idling roughness, when shut off, it doesn’t completely smooth out the RPM’s from fluctuating. I plan on doing a deep-fluid check of all the fluids on this vehicle before starting it up again to see if there’s any low levels after the vehicle cools down, as I parked it w/ hazard lights on to a flat, level ground. I will send out an update when this task is completed with status on all fluids, (or) necessary fluids that you may suggest are worth mentioning for this situation. As soon as all fluids are checked, I’ll test-fire the engine to see if the serpentine belts are running with no vibration(s).

This Vehicle has a shorted-out Odometer, the last reading from this Odometer was 148,183 miles (3 months ago upon last reading). I drive this vehicle at least 180.2 miles per month consistently.
This may not be related to my current standing problem, but this Buick Regal also has a faulty fuel gauge ONLY when the transmission is set to DRIVE, REVERSE, GEAR 3, GEAR 2, and GEAR 1. This issue in itself formed since I obtained this vehicle. ( 2 months ago)

The AC compressor may be part of your problem. Loading up the engine at idle reduces vacuum for the brakes as well as power steering pump flow… especially on older components with lots of miles on them. Shutting off the AC removes it from the drive system so you can focus on the other big power hog, the supercharger. Don’t discount failing bearings in the SC as well as a failing AC compressor.

It should not be idling at 2 to 3k RPMs. Does the idle speed ever drop down to where it should be?

I’m pondering a vacuum leak. To me anyway, the handiest tool in my boxes is a vacuum gauge. Cheap, easy to use, and can tell you a lot. Of course, if the engine is idling at the elevated RPMs you mention then a vacuum gauge is not nearly as useful.

Throttle body plate hanging up, idle air control valve problem, etc? Problems can exist sometimes that will not set a code or illuminate the CEL.

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Thank you so much for these recommendations. These seem like the best bet from what I’ve been feeling in the car’s behavior. I will try troubleshooting towards these.

The issue has been solved, it really was a vacuum leak from this part that somehow fractured its large fitting, the part is called a “Supercharger-Manifold-Vacuum-3-Tee-Vacuum” (image listed) and was what caused the brakes and the rough idle simultaneously. The large fitting was connected to a hose, connecting to the Brake Booster. The fitting on the right was cracked but not fractured, and it was connected to the supercharger bypass solenoid, which acts as a turbo regulator. Thanks to all of you and your efforts in sending me your best recommendations on repairs. image

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