Regal Boost Control Problems Causing Power Loss

Had the same issue with a 2015 Buick Regal last year. As someone with moderate experience working on turbocharged engines, I recognized similar symptoms, poor engine performance, rough idle, and high fuel consumption. After some initial troubleshooting, my mechanic found a defective vacuum switching valve affecting the boost control system. The faulty valve was causing inconsistent boost pressure, which explained the power loss and engine performance issues. The boost solenoid was actually fine, but the vacuum leak from the bad valve was preventing proper pressure regulation in the intake manifold. The repair cost me 140 Euro for parts and labor, and the difference in performance was immediate. The engine ran smoother, power was restored, and fuel economy went back to normal. No more compressor surge issues either. What engine variant does your Regal have? Also, have you noticed any specific conditions when the symptoms get worse (cold starts, highway speeds, etc.)? This info would help narrow down if youre dealing with the same root cause. The boost controller system on these engines is pretty similar across model years, so if you share more details about your specific setup, I might be able to point you toward some specific components to have checked.

Thanks for the helpful reply. My vehicle has 172149 KM and was just serviced last month. After reading your response, I checked and noticed the symptoms do get worse during cold starts. The engine performance definitely drops more noticeably in the morning, and I can feel significant turbo lag when accelerating. I suspect you might be right about the vacuum switching valve. The bypass valve seems to be making an unusual whistling sound too, which wasnt mentioned in my initial post. I will have my mechanic check the pressure sensor and the entire boost control system. The recent service didnt catch these issues, but they werent as pronounced then. Thanks again for sharing your experience with the vacuum valve replacement. Knowing the approximate repair cost helps with planning.

Thanks for the update. Those symptoms you described, especially the cold start issues and whistling sound, match exactly what I experienced with my Regal. The turbo lag during acceleration is another telltale sign of pressure drop in the system. The whistling from the bypass valve definitely points toward vacuum leak issues. When I had my vacuum switching valve replaced, the mechanic also found that the rubber hoses connected to the intake manifold had deteriorated, which was contributing to the pressure control problems. Might be worth having those checked while they are investigating the system. Since your car was recently serviced, the boost controller might have been overlooked if the symptoms were not obvious then. These issues tend to get progressively worse as the vacuum leak increases. My car went from slight power loss to serious performance issues over about 2-3 weeks. One quick test you can do: listen for any changes in the whistling sound when the engine is under load versus idle. In my case, the sound got noticeably louder during acceleration, which helped confirm the vacuum leak diagnosis. The repair should be straightforward once they pinpoint the exact location of the leak. Just make sure they pressure test the entire system to catch any other potential weak points.

You're right, the symptoms getting worse during cold starts is really telling. The turbo lag and whistling sound definitely match what I was experiencing before the repair. I'll have my mechanic do a complete pressure test of the system, focusing on the vacuum switching valve and those rubber hoses you mentioned. The engine performance issues have been getting more noticeable over the past few weeks, just like you described. I check my fuel consumption regularly, and it's jumped from 12L/100km to almost 15L/100km, so fixing this boost controller problem should help get that back to normal. I did the sound test you suggested during my drive today. The whistling definitely gets louder under acceleration, which seems to confirm your diagnosis about the vacuum leak. I'll make sure the mechanic knows about all these symptoms when I take it in. Good to know the repair cost was reasonable in your case. I'll schedule an appointment this week to get the pressure sensor and boost control system checked out. Thanks for all the detailed information, it really helps having someone who's dealt with the same issue.