Stalling HHR: Fuel Pressure Regulator vs Sensor Issues

Had a similar issue with my 2009 Chevy Cobalt. As someone with some basic repair experience, I ran into nearly identical symptoms, engine misfire, stalling, and power loss. The fuel regulator was indeed the culprit, but here's what I learned: after changing the fuel filter, you need to properly purge the air from the fuel rail system. The workshop found trapped air was causing irregular fuel pressure, leading to those symptoms. The fuel pump wasn't getting proper pressure regulation. Total fix was pretty straightforward, proper bleeding of the fuel system and rechecking the filter installation. Cost me 45 for the diagnostic and fix. Before suggesting more specific fixes, what's your: Current fuel pressure reading? Any recent fuel system work done? Specific error codes showing? Any unusual noises from the fuel pump? These details would help pinpoint if you're dealing with the same issue I had.

Thanks for the detailed response. I had it serviced at 82,000 KM and started noticing these issues shortly after. The check engine light showed code P0171 (system too lean). I've been monitoring the fuel pressure using a borrowed gauge, and it's fluctuating between 45-52 PSI at idle, which seems low based on specs. Haven't heard any weird noises from the fuel pump, but there's definitely a pressure drop when accelerating. The pressure sensor readings are inconsistent, and the engine misfire is most noticeable during morning startups. Really starting to affect fuel efficiency too, getting about 20% worse mileage than usual. No recent fuel system work besides routine maintenance. Would you recommend checking the fuel pump relay before diving into the regulator replacement?

Yeah, those symptoms on your HHR match exactly what I experienced with my Cobalt. The P0171 code plus those pressure readings are telling. When my fuel pressure sensor showed those inconsistent readings (mine was bouncing between 43-50 PSI), it was definitely the pressure regulator causing the lean condition. The fuel pump relay is worth checking, but here's why I think it's the regulator: the pressure drop during acceleration and those morning startup issues are classic signs of a failing regulator, not a relay problem. My fuel efficiency also tanked about 15-20% before I got it fixed. I wasted time checking the relay first, the real issue was the regulator wasn't maintaining steady pressure in the fuel rail. Once I replaced the regulator, the pressure stabilized at 58 PSI, and the check engine light cleared after a few drive cycles. Quick tip: while you're in there, inspect the fuel rail for any leaks or unusual wear. When my regulator was failing, it put extra stress on other fuel system components. The complete fix ended up requiring a new regulator and gasket set, but it solved all those symptoms you're describing.

Thanks for that insight. I'll go ahead and focus on the regulator first since my symptoms match yours so closely. The unstable fuel pressure readings and that specific pressure drop during acceleration really point to the regulator being the culprit. Definitely makes sense about checking the fuel rail while I'm at it. I've noticed the fuel efficiency getting worse by the day, so I want to tackle this soon. Based on your experience, I'm thinking I'll grab a new regulator and gasket set this weekend. The consistent pressure fluctuation between 45-52 PSI at idle, combined with the P0171 code and morning startup issues, seems like enough evidence to justify starting there rather than messing with the relay first. I'm planning to monitor the fuel pressure sensor readings after the replacement to make sure everything stabilizes. If that solves the pressure drop issues and gets my PSI back up to the proper range, hopefully my fuel economy will bounce back too. Really appreciate you helping me avoid the trial-and-error approach with the relay first.