Express: Rough Idle & Stalling, Fuel Regulator Issues?

Had nearly identical symptoms on my 2012 Chevy Tahoe last year. Really nasty rough idling and power issues, felt like the engine was fighting itself. After multiple check engine codes pointing to fuel delivery problems, turned out the high pressure fuel pump was failing. Unfortunately, these symptoms can also indicate other fuel injection system issues. The repair, including parts and labor, ended up costing around 1510 for the complete fix. Main signs were: Rough idling getting worse over time, Major fuel efficiency drop, Intermittent power loss, Stalling at idle Before spending money, could you share: Any check engine codes you've pulled? When did symptoms first start? Does it run worse when engine is hot or cold? Current mileage? These details would help confirm if you're dealing with the same fuel system problem I encountered. The symptoms match, but best to verify before suggesting specific repairs.

Thanks for the detailed response. Latest service was at 101376 KM and that's when these issues started showing up. I pulled the codes yesterday, getting P0171 (system too lean) and P0300 (unusual misfire). Engine misfire seems worse when the engine is warm, especially during humid weather. The rough idling is most noticeable after about 15 minutes of driving. The fuel economy drop has been pretty dramatic, getting about 25% less distance per tank now. When accelerating, there's a noticeable hesitation and sometimes a slight shudder. Your fuel pump suggestion makes sense given these symptoms. Did you notice any unusual fuel pressure readings before your repair? I have access to a pressure gauge and could check those numbers if it would help narrow things down.

Had exactly the same codes on my Express, P0171 and P0300. The fuel pressure readings were all over the place before I got it fixed. Using my pressure gauge showed readings dropping way below spec, especially at idle. The symptoms you're describing match my experience exactly, that hesitation during acceleration is a classic sign of fuel delivery problems. The car sensors were definitely picking up the lean condition, which explains both check engine codes. Quick way I confirmed it was fuel system related: disconnected the vacuum line from the fuel pressure regulator and checked for fuel inside the line. Found traces of gas, which shouldn't be there, clear sign the regulator diaphragm was shot. When the fuel regulator fails, it can't maintain consistent pressure, leading to those lean conditions and misfires. The complete fuel injection system repair involved replacing both the regulator and pump in my case. Car maintenance records showed the original parts were never replaced, so it wasn't surprising they failed around the same mileage you're seeing. The fix solved all those issues, no more stalling, hesitation is gone, and fuel economy is back to normal. If your pressure readings show similar inconsistency, you're likely looking at the same repair path.

Thanks for that information about the vacuum line test, that's exactly what I needed to know. I just checked mine and found fuel traces in the line too, so looks like I'm definitely dealing with a bad fuel regulator. Going to get the pressure readings this weekend to confirm, but with the matching codes and identical symptoms, I'm pretty confident this is the root cause. The rough idling and fuel economy issues started right after that 101K service, which tracks with typical wear patterns. Think I'll go ahead and replace both the regulator and pump while I'm at it, since they're likely original parts. Rather do both now than have to tear into it twice if the pump fails soon after. Makes sense given all these fuel injection problems you described. Really helpful to hear the repair fixed all these issues in your case. The stalling and hesitation are getting worse, so I'll get this sorted before it leaves me stranded somewhere. Will start calling around for quotes on the complete fuel system repair.